The Importance of Signing Divorce Papers

Post-nups are mostly about money and protecting assets in the case of divorce. They may be written when a couple is in crisis or concerned about the state of their union. So if you do have a shit ton of money and you just want to clean divorce, you can have a post-nup agreement that literally says we will split everything 50-50. But like also why would you sign it? Under what circumstance does it make actual actual sense for both parties?