Here's my theory.
It's about knowing these girls. At uni all the fit girls are doing things like medicine, psychology, english, fashion, photography etc etc so if you're on one of these courses then you can get to know lots of women. You're then part of the crowd, you make friends and it goes from there.
If you're doing Maths, Physics, Engineering etc. EVEN if you're a cool/good looking/good body guy you don't have the luxury of meeting nice girls day in, day out and getting to know them. I mean sure guys on these kind of courses are typically nerdier/uglier etc etc but even cool guys doing such courses miss out.
I honestly don't believe it's much to do with any of the stuff on the list. All of those things help, all of them, some more than others, but from experience I find that the fit ones typically date guys on their course etc. or in that crowd. If you're not part of it all, you miss out. An ugly guy doing medicine has more fun usually than a good looing guy doing maths.
I wish I never did Maths and Physics at uni. :-|