What don't you get about it? I can understand you having a different preference. That's normal, we all like different things. But not getting it at all? That's just weird.
I'll explain why for me. On my 24" 1920x1200 monitor, I want to be able comfortably fit two editor windows side-by-side where neither window auto-wraps the code. 79 columns works well for that. This is a function of my ability to read the text, which in turn is a function of font size, monitor size and viewing distance.
(I actually have many more horizontal pixels than you too, because I have three 24" 1920x1200 monitors. My center monitor typically is where my code lives, while my other monitors have other terminals open doing other things, like searching or compiling code.)