Beyond that, I feel like a character limit that low puts a disincentive on the creation of meaningful variable names and function names. Maybe it's a hold-over from my Java days, but I really strive to name my functions and methods something meaningful. When I'm limited to 80 characters, plus proper tabbing, plus general flow control... it becomes incredibly difficult to stay under 80.
I expect that people with somewhat normal vision will say the same.
Initially 80 was a technical limitation - you could do more, but had to make much more efforts than seemed reasonable. Then GUI allowed for more - but there was some inertia of the habit. Gradually some started experimenting with longer lines, finding cases where that's more convenient. Then code guides started mentioning line length...
On one hand, a shorter line is easier to follow with eyes - when you need to go from right side of a line to the left side of the next line, that next line is easier to find if the line itself is shorter. However the code is usually much easier to read in this aspect than prose - line lengths are varying naturally. Yet if you're trying to always keep descriptive names of variables and methods, you're not only adding some verbosity, but also more often have to split lines - and that adds to making code more "blockish".
It seems there are natural limitations - but that still depends on the particular style of the code. Have variable names just right - and you won't need too much lines in a block, so long lines could be ok. Different languages, different conventions for external libraries... It seem to be hard to put a specific number that would be both a good match with existing libraries, work (look) well for all kinds of tasks and across different languages. Sometimes one doesn't even want to sacrifice inner structure of the line - e.g., when several similar lines have important differences which one wants to highlight some spaces are often added, leading to longer lines. Or sometimes line-by-line comments are really useful (say, Minix source code) - which definitely add to line lengths.
Inside the body I'll usually stay under 75 and will split multi param function calls across lines. If lines start to overflow I'll often factor some piece out to another variable to keep it readable.
Switch cases I'll let run long if I can fit them all in as one liners. Having not worked on a shared code base for a few years I've developed a bunch of non standard habits.
Standard typographic convention is 2-3 alphabets on one line. It doesn't quite apply with a mono space font, but 3 alphabets is 78 characters.
When I'm writing hard line wrapped prose, I even prefer to keep it to 72.
I have also used 130 chars as the limit and printing source code on green bar paper. But at least to me, it just isn't worth it, IMO functions should never take more then 1 screen to view and that includes the limit of 78 chars and roughly 50ish lines. This makes code easy to grok and helps to make sure a function does only 1 thing. Not that there are not some exceptions but that is my general rule.
The 78 chars also comes from some older printers that had margin issues and if you went to exactly 80 they would wrap or add a blank line. Yea, I know, mostly stupid today, but it keeps the code super portable, predictable and very readable.
I very often put separate function arguments on separate lines.
I'm also always frustrated at the syntax of most non-Lisp languages and how difficult it can be to break lines sensibly. (Infix operators, the ternary operator, JSX, period syntax for property access, etc).
I like to use large fonts because they help me focus. And I also like to sometimes be split screen with a browser on my laptop, so "everyone has a widescreen" is irrelevant for me.
Narrow code when composed nicely still allows widescreen coders to use splitting along the vertical axis, but long lines are difficult for me to deal with with my (perhaps idiosyncratic) ways.
XML documentation in the comments — up to 180: I find the smaller wasted height is, the easier it is to work with the code.