I think this makes more sense (or at least gets more directly to the point) than any of the Stack Overflow answers. Lowercase is easier to read in print as our minds learn the shapes of the words and can interpret whole words at a time rather than letter by letter. But Morse code was originally transcribed by hand, and it is easier for sloppily written lowercase letters to be mistaken for one another than the more distinctive uppercase letters, so it became a standard to write in uppercase. This tradition carried on to teletype and early terminals until both cases were supported.
As someone who had extremely poor handwriting as a child (it is still not great...), it makes a lot of sense to me that they'd land here.
Over the years, being regularly mocked/embarrassed/reprimanded over my handwriting and often forced to re-write assignments led me to develop a weird print ~hybrid casing that substituted a fair number of uppercase forms anywhere my lowercase forms caused trouble.
(This is mostly a fallback when someone can't read my cursive, or for official forms, package labels, etc. For the same reason I also adopted a smaller number of uppercase print capitals in my cursive.)
When it isn't socially appropriate to use ALLCAPS or come across as a sTRANgE pERsoN, I have to be fairly careful/attentive when writing in print to avoid dropping into mixed case.
(I'm not a monster; I'll scale these more like smallcaps when I write them.)
It's been a few decades, but I recall having to write in all caps in my high school drafting class. We were told the all caps and the letterforms we were told to use helped legibility when the drawings are stored on microfiche.
We were still taught that in high school in the late 90s. Probably some of the last. You are correct. Here's a good example of drafting from the 1960s: https://i.imgur.com/tXozAMy.png
It's not just all caps, but a flowing, easy-to-read style of all caps.
Hard to believe people used to draw all this stuff by hand. I was never very good at it.
