Bob and Sally like each other. They like licking each other genitals. They plan to combine their genes and produce viable offspring to propagate their species.
Then government come and say, “Okay Bob and Sally, here is what the deal is.” Bob you got to be loyal with Sally and that means not fucking other females. Sally, you have the right to divorce Bob at will and collect his whole paycheck.
“If that’s what the deal is, I am out,” said Bob. Now, Sally, can’t choose Bob. Sally need to choose some idiots that do not value his freedom, which may not be her best choice. After all, it’s those who are poorer that do not mind risking all his wealth for a girl.