Why are there so many unattractive guys with attractive girlfriends?

29M. Lifelong loner. Every time I go out more and more I see the attractive women with the ugliest or most joe average guys, guys that even I could wad up like paper. This question doesn't come from a place of resentment, I've resigned myself from any form of social life, but as an observer of life and not a participant it baffles me.