What incentive do women have to be faithful and not cheat?

Im a dude and all i can say is i would never cheat on my gf. And i know alot of guys who are the same way. I also know alot that do cheat on the gf's and brag about it. I guess you just have to find that "right" guy. Its easy to generalize when youve experienced 2 already have cheated on you, but believe me there are good guys to.