This is just not the way contract interpretation and enforcement works. It never has. The law has always recognized public policy considerations that sometime

This is just not the way contract interpretation and enforcement works. It never has. The law has always recognized public policy considerations that sometimes outweigh the benefit of enforcing a particular contract. I'd be shocked if you didn't agree with some of examples of such contracts. For example, if A contracts with B for B to murder C, A cannot sue B for breaching that contract. California decided that the public policy of fostering freedom to practice one's profession outweighs the interest in enforcing contractual non-compete provisions. You may not agree. But, in the end, this is all about public policy goals. Framing the question as about the "state preventing two people voluntarily entering into a contract" isn't quite correct. The question really is whether the state should get itself involved in ENFORCING a particular agreement. Generally, the state will do so because a functioning economy is dependent upon enforceable contracts. But that is just one public policy interest to be weighed against others in particular instances.