If they don't, then the boilerplate verbiage that appears in pretty much every contract I've ever seen, which voids any provisions of said contract that are ill

If they don't, then the boilerplate verbiage that appears in pretty much every contract I've ever seen, which voids any provisions of said contract that are illegal or unenforceable without prejudice to any other terms of the contract, does. That is to say: any contract which includes such a clause can't bind you to do something illegal, just because you signed it. It's generally illegal to lie to a court, particularly when under oath.