I don't think we need a social contract, but I think it's important to understand why contracts work. So if someone breaks a contract then what? You sue. But what if you win and the other person ignores the courts ruling? Then the police come and they go to jail. Without the threat of violence a contract is just a bunch of words. Now does the threat of violence have to be provided by the government? No, there are private security companies that can do that. However, is it wise to privatize everything? It depends on who you ask. Some people would say yes, but I would not be one of them. I think if you can put a price on it it should be privatized. Things like schools and roads can easily be privatized. Can you put a price on justice? I don't think you can, and that is why I think we will always need a government backed court system.