Precisely 80 columns may be derived from TTY, but the range 80 was chosen from is not. It's around the limit of a line human can easily comprehend in one look.

Precisely 80 columns may be derived from TTY, but the range 80 was chosen from is not. It's around the limit of a line human can easily comprehend in one look. If you make it 160 (easily doable), then the line gets too wide to read. Guess why articles in newspapers were typically organized in several narrow columns instead of spanning throughout the whole page, even when the article was several pages long? And once you forget about the ridiculous idea of having few lines as wide as the whole screen, so there is a small vertical area on the left with almost all the code, while two thirds of the screen is wasted (or so you need to scroll horizontally, which is equally bad), suddenly using proportional fonts goes awry, as you need the alignment, which is a separate thing from indentation.