Sumptuary laws, which start popping up in numerous places in fourteenth century Europe, are best known for attempting to regulate people's clothing according to social class. This is true, but it's just a small part of their overall purpose and purview.

One of the ways to make a metanarrative out of the later Middle Ages into the early modern era is a "quest for order." In their broad sense, sumptuary laws were one of the tools western Europe developed for that purpose. One way they worked was, indeed, to divide society up into the kinds of neat categories it could never actually be. Miriam Chrisman examined sumptuary laws from the mid-15th century to the early 17th in southern and western German cities, showing how the different social groups delineated went from:

• Nuremberg, 1496: (1) Honorable women and young women (2) Women and young women (3) Doctors of law and knights (4) Citizens and other inhabitants (men)

to

• Strasbourg, 1628: 8 different classes, for example, Class Five (Upper): (1) Burgher families whose ancestor had been in the ruling class for a century or more (2) High chancellery officials (3) Scholars holding the licentiate or doctorate of any faculty
• And always worth noting, in Class Four (Lower): a bunch of other ranks, and then "music teachers who do not play for dancing"

And that's just it--music teachers who don't play at dances are a higher social status because dancing has the potential to get out of hand and cause disorder.

A next major way sumptuary laws sought to enforce order was by eliminating novelty. This was particular deployed in the realm of fashion. The early Nuremberg laws might not have been so meticulous about different social classes, but they got down into the dirty details to the point of setting forth specific patterns that cobblers had to use when making shoes. Wearing shoes that did not fit one of those patterns earned the wearer a hefty fine, and would probably result in the offending cobbler forced to close their shop at least temporarily (lose their market stall).

Sumptuary laws were also an economic tool for cities and countries. Obviously they might cite the wearing or using of foreign goods over local, but they could even extend (as in sixteenth-century German cities) to banning people from going to weddings in other cities. Well, with the except of being the bride or groom, of course. This kept gift money and other expenses in the home city.

Did they work? Let's go with somewhere between reddit silver and "an attempt was made." The basic foundation for each new sumptuary law was "no one follows the older ones" (although that could also be a legal trope). But there are some signs this is true. The Nuremberg law that regulated what patterns cobblers could use was the summation of a series of earlier ones that tried to ban more and more styles that people started wearing. And sumptuary laws were written and stored in archives of the city leaders tasked with enforcing them. Finally, cities did adjust their laws over the 16th century to admit certain degrees of novelty in things like clothing (such as shortening one's jacket)--the flexibility and a little bit of leeway would seem to reflect some connection to practice.

Oh, and by the way, the rule requiring long jackets was to prevent men from exposing the tops of their pants, as it was the fashion for them to stuff the front with fabric in a very, um, strategic place.