What's with all caps?

It’s taken me a while to get used to writing my sketch callouts in all caps, as I’ve been instructed in school. I used to think it was stupid and worthless, but I’ve come to realize that it looks cleaner, more stylish and much more professional. Why is this? In any other instance all caps is difficult to read and/or it implies shouting. Why does it work so well for short notes?

In drafting, we use all caps and it is much cleaner and easier to read. I think undercase is more stylized between people so each person has their own spin on what an e looks like or an a. With Uppercase, we use a more fundamental style

Perhaps because the letters are justified to the same top and bottom lines, it looks cleaner? Ironically, proper use of caps is easier to read.

I always thought it was because it looks much more like a graphic element in all caps maybe… Like a typographic “line” in the composition of the page