My theory...

Now, alot of you people might ask yourselves; Why are the ugly people so good in relationships, and why are they so nice? Why are the good looking people the ones who you don't tend to work out with? Why are they the ones who tend to cheat more?
My answer would simply be this:
The better looking people, people with more talent or people with bigger egos tend to get used to the popularity, attention etc too easily, they tend to take advantage of it by doing things such as cheating.

Where as on the other hand, the not so good looking people and unpopular people don't get the chances that these so called good looking or "cool" people get; Instead for example, they get leftovers of people who have been hurt, they get desperate people, they get all sorts of people.

But who's to say, if the not so good looking people were actually what society considers "hot", or "cool", who's to say that these people would not take advantage of the so many more things they get offered in life?

Life is what you make of it.