I can't say for sure, but I have spoken to a lot of banks over the years, and I think most (if not all) of them get them signed. It doesn't have to be signed, and a verifiable system is evidence of compliance, but a signature is nearly irrefutable evidence of compliance. A verifiable procedure can become your word against the customers in a dispute. And juries often are not friendly to banks. Do you not send them electronically when possible?
Only two things that money can't buy, that's true love & homegrown tomatoes