I think men marry in the hope of binding their partner; fat chance. Marriage gives the partner a claim on a big chunk of the man's assets, so it incentivizes women to divorce their husbands. The great majority of divorces are initiated by the wife. I'm not sure why women marry; I'm not a woman, but maybe the reason is the same.
Marriage is an outdated custom. People should learn how to live together without submitting to these ancient legal customs.
Source: I'm twice married, and twice divorced; both partnerships lasted 15+ years. I'll never marry again.