A friend of mine is now married to a woman he dated for a bit late high-school (beginning of college) before she dumped him because she wanted to "have fun" while in college.

Last time I hung out with him and her she was very upfront about the fact she basically broke up with my friend to get fucked by as many dudes as she could before she decided to get back together with my friend.

It's as common as it gets. Women in their youth don't want "nice guys" for boyfriends. Women want to ride the cock carousel and then only want "nice guy" boyfriends after they get ugly and can't ride the Chad Cock Carousal as easily.

Alpha fucks. Beta bucks. Women fuck attractive men in their 20s while the women are hot then as the woman's 20s wind down they negotiate with an average looking beta dude for as many resources as they can. They typically aren't nearly as sexual though because the relationship for the woman is about getting money and time/effort/resources from the man for as little work (sex) as she has to do. She's not typically attracted sexually to this guy because she's attractive sexually to the men she fucked when she was younger and hotter but can no longer pickup easily enough.

And for the record, that's exactly my friend's situation. The girl who dumped him to fuck other men that he's now married to apparently "isn't a sexual person" and they have a dead bedroom. Meanwhile, he drives like a 20yo beater vehicle while his wife drives a brand new SUV because that's all he can afford while he slaves away making her SUV payments and his mortgage payments on the big house she convinced him to buy.