There are plenty of good reasons for short line lengths. Two factors constrain the max line length down to something not much more than 80 columns: side-by-side diffs and waning eyesight.
In-line diffs mix the flow of change in with the flow of execution, both going down the page. Side-by-side diffs makes those two axes orthogonal. With decorations (either in a terminal or a code review tool) even 80 column code requires a fairly small font. Editing two panes of code only needs 161 columns but a decorated patch might be more like 170.
The point font size is its height in increments of 1/72”, and most fonts are half as wide as their point height. The largest font one can use on a 27” monitor (24” wide) is 20pt. My eyes get knackered at anything smaller than 18pt.
In-line diffs mix the flow of change in with the flow of execution, both going down the page. Side-by-side diffs makes those two axes orthogonal. With decorations (either in a terminal or a code review tool) even 80 column code requires a fairly small font. Editing two panes of code only needs 161 columns but a decorated patch might be more like 170.
The point font size is its height in increments of 1/72”, and most fonts are half as wide as their point height. The largest font one can use on a 27” monitor (24” wide) is 20pt. My eyes get knackered at anything smaller than 18pt.