History of credit cards.

Signing credit cards has always seemed a bit absurd. Any thief that cared to forge my signature has a perfect reference right on the card. Five minutes practice should be enough for anyone to approximate a signature to the point that no clerk is going to challenge them.

On the other hand, if someone steals my card and the signature isn't on the card, then they'll have no idea what my signature looks like and it will be obvious from the receipt that the purchase was fraudulent.