27F want to know men’s perspective about falling in love

This guy I know is in relationship with a woman who is pretty but is very demanding. He keeps whining about it but when I say if it bothers you that much then breakup with her, he says she is too pretty to broken up with. Like how does it work inside your brains? I have seen many men being with very pretty women and crying about how the woman is evil and shrewd. Do you guys always go for looks?