My question would be, what is that signature supposed to represent?
As a quick study with a totally inadequate sample size, I looked at the credit cards in my wallet and my pilot and CFI card.
Of the 3 credit cards, 2 said "Not valid until signed" and the other didn't have anything like that. It had a signature box, but nothing saying I had to sign it. Maybe I don't?
On the 2 FAA certificates, it just says "Signature of Holder".
But what does signing it mean? I don't know that I'm agreeing to anything by signing my pilot certificate. By signing my credit cards, I assume the idea is that I am signing the contract of use and agreeing to the terms and conditions. But there's nothing like that for the FAA certificates.
I mean, whether or not I sign my FAA certificates, I'm still required to follow the FARs and other pertinent regulations. No DPE or any other official has actually ever compared the signature on my pilot certificate to a known signature of mine (like on a signature card at the bank) to prove that it was actually MY signature, nor can I imagine they'd do that even if I was undergoing some kind of certificate action (like suspension or revocation). So what exactly is accomplished, legally, by signing, and what is the benefit?
Seems to be just an outdated or misapplied requirement to me.