This should be the default. Today, many spouses are gaslit by their partners not to accept a prenup and are destroyed as a result. There is an incentive for these partners to their turn their spouse's love and trust into financial deals where they have more leverage. This is wrong and should be prevented.

Because divorce is such a simple contract to break, initiators are incentivized to break it once they have secured other, better deals elsewhere. There is very little cost to the non-bread winner, especially if they spend more time with children by default.

This is not like how any other contract in the world works. Simply breaking a contract and walking away in the middle of a deal is not allowed without heavy penalties, and these penalties are incentives on both parties to A.) sign good contracts in the first place and B.) honor their end of the bargain.

The modern marriage contract is the equivalent of paying a phone bill, then deciding you don't want to pay anymore and when you do that you keep the phone plan with no additional cost. The only thing holding these contracts together is the good will of both parties, and that is not enough to ensure good behavior.