This may be less of an issue with code, due to its structure, but I still find it much easier to read 80 column code than code that stretches across the screen.
If I'm reading code in an 80 column terminal I prefer the line breaks to come from the human that wrote it, to show and reveal structure, rather than having it arbitrarily broken at 80 columns by the editor.
Another reason is that most of your code won't stretch across the screen, but you need your window sized for the small amount of code that does, losing a bunch of screen estate to empty space.
But I don't worry too much about it.