What about us poor slobs whose vision is less than perfect where the 80-character line is too small even when it takes up the entire width of the display? The way zooming is implemented in the mobile browsers, we must horizontally scroll back and forth for every line we read.
I don't think my glasses can correct my vision well enough to be able to read 80-char-wide text on a smartphone in portrait mode. I can't say for sure because I don't own a smartphone--partly because I worry about being able to read web pages on it without regularly resorting to the aforementioned tedious horizontal scrolling.
I always wear my glassses when I'm using my iPad, which is in landscape mode almost all the time (the exceptions being the rare apps like Uber's that won't do landscape mode).
