>>82315983
Because to you she would everything, to him she's just another young slut. She doesn't want to be the everything for a man her age, she just wants to have some fun. He doesn't want her long term, he just wants some fun. Maybe she's broke and he's got a nice stable income. Maybe he didn't get any when he was young so he's living it up. Maybe he's always slayed pussy and now he's just keeping it going because he can. Maybe she just likes older men and he's willing and able to support her.
He can't raise a family with some random girl who fucks random older men, that's not a mother or a home keeper.
Age gap relationships have a terrible track record. It's not impossible of course but that is result when both sides are using each other and there is no "love". Just lust and infatuation.