I've never understood why people think social contract theory makes any sense. It's not a contract at all so the very name is misleading. From wikipedia:

According to the will theory of contract, a contract is not presumed valid unless all parties voluntarily agree to it, either tacitly or explicitly, without coercion. Lysander Spooner, a 19th-century lawyer and staunch supporter of a right of contract between individuals, argued in his essay No Treason that a supposed social contract cannot be used to justify governmental actions such as taxation because government will initiate force against anyone who does not wish to enter into such a contract. As a result, he maintains that such an agreement is not voluntary and therefore cannot be considered a legitimate contract at all.

The belief in authority is a myth.