This Doesn't Look Right

I went to the Big Box store to get some stuff. I swiped my credit card in the machine. I signed for the purchase with the stylus on the device's little screen. The cashier asked to see my credit card. She compared signatures.
"This doesn't look right. Can I see an I.D?"
Flummoxed, I produced my driving license.
"I need to get the manager. None of these signatures match."
"Come on!" I retorted, angrily I admit. "How can any of these signatures match? One is written on paper on a desk and then copied to the license. One is written with a sharpie on a little box on the credit card. Be careful not ot cover the three digit code! The third is written with a stylus and no support for my hand."
She looked again. "Close enough."
I went home.