Why do men with beautiful, intelligent wives have extra-marital affairs?

You know who (it actually pains me to write out his name) is just one among a seemingly endless string of rich, talented and famous men who have extra-marital affairs with women, despite the fact that their wives are clearly beautiful, intelligent and giving women.

I remember Bill Maher once arguing once upon a time on Politically Incorrect that, “Let’s face it…all great men cheat. That’s what great men do.” (Paraphrased, of course.)