80 columns wastes a lot less screen space.

Even in 120 column codebases of my experience, about 90% of the extra 40 columns were blank.

I always liked 80 columns. In the place I live now, I have two windows, each with a glorious view, so I keep my monitor vertical so it doesn't block either window, and 80 columns is great! (I don't even like vertical monitors, but I really love the view.)

I should add that I truly hated punched cards, and would have probably left the field if that had continued to be the form of programs. :-)