Signatures are not really anti-forgery proof as most people expect...

Instead they are protected by law. If you sign something claiming to be someone else, you have broken the law.

That's why credit cards required a signature for a long time, yet nobody ever checked the signatures on the receipt vs the card. It isn't hard to fake someone else's signature, but doing so is a crime. Using someone else's card without a signature would just be a breach of the T&C's, but not a crime.