Credit card signatures are intended to be verified on the spot. That's why the back of the card says it isn't valid until signed. The cashier was originally supposed to compare the signature on the card to the signature made at point of sale to verify the CC holder's identity. https://consumerist.com/2014/07/19/10-answers-to-credit-card...
Of course this doesn't happen, and for good reason too since the signature made on a resistive touchscreen ends up looking nothing like that on the credit card.