Actually, signing the receipt has everything to do with fraud. If you use a credit card in a transaction you are required to pay regardless of whether you sign an agreement saying so. The difference is, if the merchant does not collect your signature, they are liable for any chargebacks AKA reports of fraud whereas the bank would be if the merchant did collect the signature. [1][2]
My point in bringing up the signature line on the back of the card is that, while it might not meet your personal standard of effectiveness, it is an example of "a pin at checkout is a good one to reduce fraud. However it is more work for the consumer, and reduces the bank's liability."
Signature verification is an old-fashioned, and perhaps imperfect, nonetheless established method of security.
If you have ever used traveler's checks, you will know that they also use signature-matching as the method of security/verification.
Because if you did not sign, there is no written contract for that transaction, so there is far less of a case that the charge is valid. Regardless of what the signature looks like, you are liable if it was you (or someone you authorized) who signed and you are not liable otherwise. You are even liable if you charged for the transaction but did not sign - there is just no written, signed contract, so you are presumed not to have agreed to the charge.
None of the above is legal advice as IANAL, however I do believe it is correct.
Do you really think a merchant can verify those electronic scribbles on a tiny, crappy pen input device? No. Any mark made by you with the intent to sign is a legal signature.
My point in bringing up the signature line on the back of the card is that, while it might not meet your personal standard of effectiveness, it is an example of "a pin at checkout is a good one to reduce fraud. However it is more work for the consumer, and reduces the bank's liability." Signature verification is an old-fashioned, and perhaps imperfect, nonetheless established method of security.
If you have ever used traveler's checks, you will know that they also use signature-matching as the method of security/verification.
[1] http://www.npr.org/templates/story/story.php?storyId=9227832... [2] http://minnesota.cbslocal.com/2012/02/14/good-question-why-d...