When everything is going great in my marriage, I don't need a reminder that I'm obligated to stay with my wife. It's when things suck that my ring, my vows, and my marriage certificate are beneficial. They keep me there because I know that if I break them, I'd be a liar. And I know my wife will stick with me when things are tough because she's made the same commitment.
If marriage is silly, are contracts between employers and employees and between founders and investors also silly? If not, why?