I'm not sure if you are agreeing or disagreeing. The social sanctioning is part of how a society sustains a contract. If there were no contract, you could be married in the morning and walk away from it in the afternoon.
In modern western societies, we have alternative ways of sustaining contracts, such as are provided by the law courts. However, if people entered into a formal contract, but the content of that contract were abhorrent to the society, the courts would not sustain that contract.
Compassionate conservatism - bringing you a kinder, gentler torture chamber