The real reason is family law hasn’t changed in decades and the invention of no fault divorce. Why would a man want to get married when the divorce rate is ~80% and he has to give up half his assets?
Discussion
Replied before I read the comments. Exactly right. No fault divorce is 100% a violation of contract law; if one side can nullify a contract because they are no longer "feeling it" then it's not a contract, but if they can nullify the contract for no reason AND lay claim to all communal property that is taking it over a barrel with no vaseline.