A "bad bytch" have tendencies to make the man around her feel inadequate and not appreciated, since birth pretty girl been getting everything her way, and expects as much from all of her relationships.
But men are men and when he doesn't feel appreciated, or he hitting it and she acting like she could be doing something better than having a consistent sex life with you, a man will seek that validation and sense of adequacy elsewhere, even between the legs of the ugliest of the ugly.
Thing is with Ms ugly, she making him feel like the shyt, with funky overweight white girl, she making him feel like the shyt, with boney no body shape having white girl, she making him feel like the shyt, and pretty girls feel it's beneath them to make their man feel like the shyt. So pretty girls get cheated on.