I thought marriage benefited men? Maybe guys who like to get around don’t want to be married, but they could marry a swinger, and still do that. Maybe they are loaded and want to keep it all?

But for two regular people in a heterosexual marriage, in general, men benefit more from the arrangement. Meaning both people do benefit - economy of scale, split work, but generally speaking men gain more than women, the split isn’t even in most cases.

My real guess is that it’s nostalgia for a situation they would not have even if they had not married. They misremember their youth.

If they just mean legal marriage and taxes they have a point. That can be cheaper if you stay unmarried, it depends. We pay more married than we did unmarried because we each were single parents, and our earnings are close to the same amount.