The fabled "five paragraph essay" that you describe--tell 'em what you're going to say, say it, tell them what you said--absolutely has its place...in high-school level writing. It's an excellent way to force unpracticed writers to think about the structure and the logic of their argument. It ideally helps the writer be clearer about the actual point of the essay in words. Yes, this is a skill people have to learn: how to translate jumbly inchoate thoughts that they just know into verbal or written prose conveying that just knowledge to another person. It's as much about training newer writers how to think as it is to write.

Notice I said "high school level" and "unpracticed." Regardless of actual education achievement, that's neither the AskHistorians answer base or our readership. If you're inquiring about history on the Internet--yes, even if your question is prompted by your latest go-round with Europa Universalis--you're already a bit above average, and the depth of writing and thought on AH bears this out even farther than I would have thought possible on the Internet.

So let's take a look at more advanced levels of writing, and move specifically into history writing. You've got books, you've got articles, and you've got talks/lectures. These can all be formally academic or more popular (American Historical Review versus New Yorker; academic conference versus invited speaker at the library). In both of these formats, you'll see a pattern.

Books usually have an introduction that lays out the rest of the book. It will say the argument, if it's an explicitly argument/thesis-driven book, or it will convey the gist of its perspective if the argument is something more ingrained like "the Reformation was primarily an intellectual (religious, cultural, etc) change driving other changes." Often, it will give you an overview of how the rest of the book will go. Sometimes "Chapter 1 will" and "Chapter 2 builds on", or "the essay by Dyan Elliott will investigate" "Then the chapter by Ruth Mazo Karras will explore".

Moving down to the article level, you'll usually find in the introduction a general thesis statement, which is enhanced by a more specific/concrete one at the end. It's pretty rare to get a 'projected outline' in the introduction--one of the reasons for the popularity of sections and subheadings. Not unknown, but certainly far less common than book introductions. (Also, some articles will genuinely not tell you their point upfront. Literature people who talk more about theory than texts, looking at you.)

At a conference paper or a talk, you'll probably hear a thesis statement at the end. I've heard them upfront occasionally and sometimes written one in at the beginning. Far less frequently than in articles, though. And I don't think I've ever heard a verbal outline of "this is what's coming" upfront.

What's the difference?

Length.

You just have fewer words in an article than a book; and fewer words in a talk than an article. Cutting introductory material preserves the core of what you're trying to say--the essential details for people to understand. You still convey your message, and ideally the audience takes it away.

Us, meanwhile? My dude, we're on reddit. 10,000 characters in a post is not much for the historian who is used to 10,000 words in an article. And we're in the digital realm where 140 characters is more and more people's speed. Introductory material is going to do two things: (1) Make the whole thing longer, which means readers are more likely to lose interest, click away, glaze-over reading without absorbing, and (2) satisfy quick comers who will lose interest and click away.

To put it another way: I'm not here to give you storebought Weight Watchers "brownies" that will leave you questioning why you ever liked brownies in the first place. I'm gonna bake double fudge brownies, and I do hope that you will take the time to enjoy them just like I had fun making them. And you'll go away feeling a lot better about the brownie you just ate--and about brownies in general.

Excellent answer - of course - by /u/sunagainstgold; a few thoughts - briefly!

Academia thrives on critique and response, and so academics are trained to poke holes in the work of peers. Historians are no exceptions, and in fact, the inherent diversity and complexity of humanity exacerbates the situation. The brief, eloquent Pirenne Thesis inspired thousands more words on how his simple idea needed to be refined or contradicted. The same thing happened with Frederick Jackson Turner's Frontier Thesis. Simple answers can become the red flag waved in front of the academic bull (if you'll pardon the expression!).

Graduate students are trained to dismantle the work of fellow graduate students. This is a healthy birthing process because it is important to be able to use the method of peer review to help colleagues with their work. During the birthing process, this can go overboard, and some of what you see here may be the result of young scholars attempting to avoid the cattle prod - because it hurts!!!

Let's consider a simple example: 'Have people consistently in history viewed the sun as hot?' Well the answer is, of course, 'Yes.' But nothing is that simple, so a better answer is 'Yes, [and here comes the most important word in a historian's vocabulary] but perception of heat and the sun can be different. An Inuit is going to perceive solar heat differently from someone in Sicily. Let me elaborate...' and so we go down the rabbit hole.

It would be great if historians could settle on the sort of grand unifying theory that physicists seeks (and occasionally they believe they have found). But humanity is not likely to be explained by the equivalent of E=mc2. It is too complex, and it consistently requires caveats.

Answers provided here are often attempts to cover one's self. Occasionally, we see that graduate student urge to go on the attack; that is an expression of the baptism by fire that historians invariably endure in training in seminars where peers challenge positions taken as ways of perfecting the critical mind. Whether with venom or with kindness, peer review reminds us all that nothing is simply and complexity is the name of the game when it comes to history!

If I may point out another issue, in addition to those already discussed here, often people looking for an answer think they know what they want to know, but they don't. A short, concise, to the point answer - which is a great thing among "peers" and works well as a knowledge transfer - may have the effect of confirming their "mistake".

For example, if a specific question is asked like "Was the inclusion in Giovanni Giolitti's national block an important point of the fascist rise?"; a proper answer may be: "Yes; it allowed the fascist into parliament and made them more palatable to the establishment. Because... In fact... Therefore..."

Yet, why he did it? That's a key point of how actually they became palatable to the establishment but also a consequence of the nature of post unitary Italy, the idea of the State, the commonly held views on organized violence - and if possibly how those views were shared by the population. Did he really have to? Were there alternatives?

Back in high school, I would have answered with the short, self consistent version; my teacher knew it already.

Here the people looking for an answer don't or I am assuming they may not. I need to explain properly and if they leave with the feeling that they know less than before... well, that's the entire point: they found out another thousand questions that they may ask - that's why sources are included; if possible, not to show off or just to prove knowledge but to support interest end encourage the reader to build their knowledge they way they see fit.

This kind of work requires time - a lot of time for me. Sometimes it turns out right and sometimes it doesn't; but I'd rather write a poorly structured answer than one that gives the reader a wrong feeling of having "completely understood" the issue.