The problem with the 5 paragraph essay is that it isn't a rule of thumb, it isn't a good guide, and it is never appropriate. Except maybe as a brief skeleton to build a student's understanding of longer-form writing on, to be discarded in the next assignment or two, but to be grading outgoing seniors from high school on it (and so rigidly!) is an atrocity.
Try to find one in the wild, one that was never a school assignment (so no published student homework or anything). Go on. Try it. Find one on HN comment page. (A different page. I'm sure someone will at some point float a 5P essay here as a response to be funny... the thought crossed my mind to try to do this exact criticism in this style, but ye gods is it a worthless style to communicate in and I didn't feel like sacrificing my point for the meager humor that would be produced.) Find one in a newspaper or magazine. Find one in a blog post. Find one in a well-regarded historical work on philosophy. And remember, it's not just a mere "it has five paragraphs", but a very proscribed schema that is at least:
1. Thesis paragraph, 5 sentences
2. Support point #1, 5 sentences
3. Support point #2, 5 sentences
4. Support point #3, 5 sentences
5. Restatement of thesis, 5 sentences
I won't guarantee you can't. I will guarantee that you will be looking for a long time.
There is a reason for this.
You're right - the format doesn't show up outside of school. And if we were being bombarded by 5 paragraph essays in the "real world" then we'd certainly have a lot of justification to this entire thread. But we don't. You just proved it. So what's the issue here?
(See also our math curriculum's ability to convince people that "=" is not symmetric by the repeated hammering of "1 + 4 = ___"; we think we're teaching them math and using "equals", they're learning that the "=" symbol means something more like "simplify and reduce" and that it has a direction. Grab three random people with the "usual" math education (i.e., not programmers), and see if they will agree that "1 + 3 = 2 + 2" (you may need to put an underline under the 2 + 2); I think you'll find a lot of them insist that is "wrong" and the right hand side "should/must be 4". And that's just one example.)
It definitely is a rule-of-thumb. You may not think it's a good one, but it still is one.
> it isn't a good guide, and it is never appropriate. Except maybe as...
Claims as strong as those are rarely true.
One might as well try to defend scales as being a valid form of music that should be performed in front of thousands of people. (And I mean literal, raw scales, not something that works a scale into a piece, for which there is no meaningful equivalent in this writing context.) Even if someone did that, it would be as some sort of artistic comment on listeners or the nature of art or something (see 4'33"), not because they have any reason to be performed in front of an audience.
By the way, since this may seem a bizarre amount of passion on the topic, what cheeses me off is that we TEACH this as the One True Essay Format. (See the beginning of the linked story.) I just can't believe the unnecessary harm we do with this. Even with my relatively low opinion of the ability of current formal schooling to educate, this still surprises me as a bizarre choice. So if I sound like I'd like everyone reading this to come away with the idea that this format ought to have a stake driven through it and you should never use it, it's just my feeble attempt to undo years of terrible schooling in a handful of paragraphs.