As soon as I married my wife and we went back home, we realized that we just threw a party and life continued all the same. I am shocked how complicated we, people, can make our lives to ourselves. Is the need of a marriage only related to our human wish to belong? Like you said: in the married men's club. I can think of only a few practical use cases:

- if your sweetheart is another nationality, you'd want to lawfully get him/her abroad;

- if you have children, they would get double citizenship (in some cases);

- if you're spiritual, you might want to get God's blessing in a temple as a sacred bound;

- worst practical case: not enough trust in an eventual division of property upon a break up.

I'm not familiar how laws work on divorces in the USA, but it sounds very hard and complicated. Especially in the case of two smart men who can make peace and consensus, even not wanting to be together any longer.