Why uppercasing every single word in topics became so popular?

Here in Canada at least, I was taught in elementary school to capitalize all important words (i.e. other than and, or, at, in, etc.) in a title. Is it taught differently in other places?
- It's taught that way in the US as well.
- In the uk they just teach us about proper nouns
  
  Funny thing is, I'm Canadian, and proper nouns was all I was taught as well. "The, in, and, etc." look weird when they're capitalized and not also the start of a sentence.

It's called Title Case. There are different rules depending on which style manual you're using. Some people just capitalise everything. Some people don't use it at all.
- and some people like to SHOUT, while others like to ScReAm
  
  In all fairness, alternating caps is read in an extremely different way. It mimics an undulating high-low pitch that is frequently used for mockery in English. Can also be represented with a tilde, usually in a friendlier manner.

It something that always has been. Ben Franklin's Poor Richard An Almanack from 1739 uses title case. It was used in illuminated manuscripts written by monks
You're asking something that probably comes from a wide array of reasons that dates back literal centuries, even millennia.

You mean like how titling works? Like book titles and shit? Lmao I don't see what else you could be asking. Did you think it was some modern trend or something instead of how literary works have been titled since forever?
- Well for me, I don't care so much to the WHEN. What I want to learn is the WHY. I'm feeling it'll be a deep rabbit hole.
- its called no stupid questions mate, no need to be a dickhead. as other people have said op probably isnt a native speaker and lots of other languages don't capitalize titles the way we usually do in english.

In print, you can use all-caps to produce a large, attention-grabbimg headline and reduce the leading (line space) without worrying about font ascenders or descenders interfering.
Online, it's just shouting.

I hate it - whoever invented title case needs their head checked. It makes it far more difficult to read.
For short titles it's fine which is probably the use to be fair, but when people on reddit/lemmy write a short essay as a 'title' man that is annoying.
- tIME tO uSE aNTI tITLE cASE
  
  This is somehow less jarring. Didn't expect that lol.

I tend to do this without even thinking about it. I think it looks nice though.
- Costs me lots of lost time editing the body of my email because I instinctively do this capitalization thingy everywhere. Tis a plague.

See? That's what you get when you insist to write everything in lower case with weird exceptions (I is capitalized, you isn't, narcissists...) People make up even weirder exceptions. That's on you, sloppily simplistic english grammar!
- You vs I is a possessive noun thing. I is possessive, you is not, so I gets capitalized, and you does not.

Don't you mean "Why Uppercasing Every Single Word In Topics Became So Popular?"
- Short, common words like "in" aren't capitalised