I am assuming you are just talking about the sunni shia divide. Part of the reason is because theological differences are handled differently in Islamic communities than in Christian ones. Unlike Christianity, theological differences don't generally man a new sect forms. Specifically in Sunni Islam there is a trend of lots of theological differences but still being under an umbrella of Sunnism, like the term Protestant refers to a large number of churches with different theological doctrines. This is because while there is a position of Caliph, it wasn't a theological position generally held as being able to enforce doctrine, so the local scholars (like rabbis) would sit around and debate doctrine and run courts with a cacophony of voices and ideas. Take sunnism for instance, there are four major legal schools, atleast three theological schools, dozens of Sufi orders, modernists of various Stripes, Wahhabism (a hybrid group), and a multitude of salafi groups, and the mostly extinct mutazillas, yet they are all generally just called Sunnis because the method developing their fortune stims from the Sunnah (traditions) of Mohammed.

On the otherhand Shia have a more hierarchical order with more clearly defined breaks between groups, generally based on the number of Imams (descendants of Mohammed they believe are rightfully guided and inspired by God). The three major groups are Fivers (Zaydi, found mostly in Yemen), Sevener (Nizari or Ishmali, found around the world, lots in India) and Twelver ( this is by far the most common Lebanon, Iran, Iraq, Bahrain, Saudi Arabia, and Qatar either have majority or large minorities of this group). Twelvers are the largest group along Shia in the modern period because of the forced conversion of Persia in the 16th century (from Sunni to Shia). In addition to these mainstream Shia sects there are the Alawites of Syria (have very u unique bells involving a trinity of God, Mohammed, and Ali, and have been working toward mainstream Shia acceptance in recent times), Alevi in Turkey (either a folk religion mixed with Shiism, or something else) and the Druze of the Levant (generally considered a separate religion but congress from Shiism)

In addition there the Ibadi of Oman who are neither Sunni or Shia but a third group. And the Amhadiyya from India and Pakistan, which is a 19th century reformation movement similar to Mormonism in Christianity. And Bahia from Iran which sees itself as a separate religion but a continuation from Islam.

Basically what I'm saying is there are many many sects of Islam that get obscured because they are grouped together in clear groups to make it simple. Also a history of keeping different theological differences within the umbrella of Sunnism. All in all just taking about Sunni and Shia as the different sects is like saying there are only Protestants and Catholics, each name belies different internal separation (Catholics for example have many different "rites" under one banner and atleast one breakway group)

Edit: excuse my spelling mistakes, I'm on mobile at the moment

It depends on what you mean by "sects". Judaism by some measures has no sects, by some sects several. One of the main divides is between Ashkenazi and Sephardi/Mizrahi... but this is a difference in custom (minhag). They all (generally) recognize each other as equally full Jews. There were few real divisions before the nineteenth century, other than the various divisions caused by Messiah claimants, most notably Sabbatai Zevi and Jacob Frank. When Yisroel ben Eliezer, better known as the Baal Shem Tov or the BeShT, began teaching what became Chassidus/Hasidic Judaism, this was a major division among Ashkenazi Jews. Though it was a rupture for a few generations, today it doesn't really matter and people would treat it as different "customs" rather than different sects. And today there are dozens of Hasidic courts, each with their own slightly different customs. A similar thing happened when the movement that became Modern Orthodoxy emerged. But while there are several different kinds of Orthodox Judaism (Modern Orthodox, Misnagdim/Litvish the non-Hasidic non-modernishe Ashkenazi Jews, many Hasidic courts, and a variety of different Sephardi and Mizrahi minhagim) each with slightly different customs and legal rulings, they wouldn't generally recognize each other as different "sects" for the most part. Just last Friday I had dinner with a Hasidic rabbi, and one of the other guests was a Modern Orthodox rabbi, and they repeatedly deferred to each other.

Then there are two other categories of possible "sects": the first are perhaps not even Jews, the second are Jews who are just doing it wrong. The Samaritans and the Karaites, both very small groups, have an ambiguous place in Judaism as groups that maybe aren't Jews, but definitely resemble Jews. The former category includes Reform/Liberal and Conservative/Masorti Jews. They have a very different approach to Jewish law from the Orthodox, and while the Orthodox recognize that they are Jews, and they recognize the Orthodox as Jews, the Orthodox don't generally recognize the Conservative/Reform rabbis as "real rabbis", though obviously this is a complicated situation. The Orthodox definitely don't recognize their conversions, for instance, and the Conservatives won't technically recognize many Reform conversion. Then just to make things complicated there are also the Humanistic, Reconstructionist, and Revival movements, but we'll just bracket those. But there's, at the same time, a tremendous amount of movement between the different groups and they don't have the rigid lines you associate with sects. In the past three years, I've been to services conducted by Humanistic, Reform, Conservative, Hasidic, Modern Orthodox, and Sephardi Orthodox congregations. Then again, many Christians "sects" aren't really "sects", but denominations these days.

But in Islam, too, you have within Sunni practice four major divisions of the four major madhdhabs (juridical schools--like Sephardi and Ashkenazi). As a non-Muslim, I can go to any mosque in Turkey but can't enter most mosques in Morocco. Saudi women are expected to cover their faces, but that's much rarer elsewhere. Those are differences in madhdhab. There are even slight differences in prayer. And as late as the fifteenth century, there was a possibility that some form of Shi'a was going to be recognized as a fifth madhdhab.

Among the Shi'a, there are a great variety of different groups. The Twelvers of Iran, Iraq, Lebanon, and Bahrain are by far the largest Shi'a group, but not the only one. There are Alawis in Syria and the Hatay province of Turkey (this is the group that the Assads belong to) who are known for being very secular. There are Alevis in Turkey, both Turks and Kurds, who are known for being even more secular today and were often viewed as irreligious in history (they are famous for not fasting during Ramadan, to give a well cited example).

Twelvers are known as Twelvers because they had Twelve Imams before the last imam "occluded" himself and became hidden, but there are a variety of other groups that have different numbers of imams. The Seveners, for instance. There are several groups, like the Agha Khanis and various kinds of Bohra, that still have living imams. Here's a chart to keep it all clear. These groups are more sect like because they generally won't switch between groups, but you do see a lot more intra-Shi'a cooperation at the geopolitical level, at least.

Two last categories worth mentioning. The first is the various Sufi brotherhoods. These functioned, in a way, like the Hasidic courts, where they all generally recognize each other as real, compete with each other for new members, generally don't switch between groups, and generally are led by one Sheikh/Rebbe (at least in theory/historically). These groups have their own traditions for prayer, worship, dress, ritual, etc. Their own texts they study, etc. And while a Satmar Hasid generally won't became a Bostoner Hasid and a Bektashi Dervish won't become a Mevlevi Dervish, the daughter of the Bone might marry the daughter of the other and the leaders might even consult each other in certain circumstances.

The last groups worth mentioning are the groups that are ambiguously connected to Islam. Members of Baha'i faith no longer describes themselves as Muslim, but Baha'i definitely began as a split from Islam. Ahmaddiya are more ambiguous, as some groups consider some Ahmadis to be Muslims, while others consider them to be Muslims but heretics, etc. etc. Again, the two main Ahmadi communities clearly split off from Islam.

But what I mainly want to say is that Protestantism is the weird one. In Christianity, you have a whole series of splits that are political fights cloaked in theology (the split between the Syriacs and everyone else, then the Oriental Orthodox vs. Apostolic Orthodox Catholic Church, the finally the schism between the Orthodox and Catholic churches) for most of its history. Then, the Protestant Reformation comes, which is a serious theological as well as political challenge to Catholic Church. However, après Luther, le déluge. The way that Protestant Churches are organized, particularly in the English speaking world, is pretty unprecedented. Reform Judaism, and later Conservative Judaism, are heavily influenced by this sort of Protestantism, but historically it's pretty unique. If that's what you have in mind, I'd be very comfortable arguing that Protestantism is the "weird one", especially today when most Methodists, Baptists, Lutherans, Episcopalians, etc. might have great difficulty explaining what made their groups different.