They are probably not illegal to put into a contract, even if they are illegal to enforce. I don't know about CA specifically, but we have similar statutory rig

They are probably not illegal to put into a contract, even if they are illegal to enforce. I don't know about CA specifically, but we have similar statutory rights UK, which is why employees largely ignore them by signing the contract with the non-compete clause in. The point still remains. There is sufficient contractual legalese that is backed up by threatening lawyers letters that stop some or most of the staff leaving and going elsewhere. That is enough for the deal to go through.