help me please..

I was stalking a few of my friend's profiles on a social networking site the other day. I went though the profiles of some unknown men and women who were attractive to catch my attention. And strangely there was a common factor which I somehow figured out. And so I want you to help!
Why do most good looking women date or get married to ugly or not so good-looking male partners and vice versa?
Is it 'cause love is blind? Or it is some sort of a rule of nature? Or is it planned that in a relationship, only one mate gets to look attractive, unless you are too lucky?