I went to the post office the other day and tried to use my credit card. The lady behind the counter wouldn't accept it because it wasn't signed. I offered to show her my ID, but she said that the card would still need to be signed. So, I signed the credit card, and she processed my transaction.
She then handed me the sales slip to sign. When I handed it back to her, she took it and compared it to the signature on the back of my credit card. Satisfied that they matched, she gave me my card and receipt and wished me a nice day. She never looked at my ID.
I would have to be the stupidest thief on the face of the planet to forge the signature on two documents, one right after the other, with different signatures. What kind of security is that really providing me?