There is a HUGE percentage of gun owners who believe that all guns bought at a gun store are registered. I can't count the number of times I've heard someone say they wanted to buy used from someone so it wouldn't be "in their name". These aren't criminals, just regular people who are deathly afraid that Obama & Co. are coming for their guns.
I may be among the ill-informed, then. Or maybe I'm just confusing "registration" with "trackability". But when I buy a gun at a gun store, isn't my name then associated with that gun in the dealer's bound book? I agree that's not the same thing as a statewide or nationwide "registration", but it does connect the gun to me, so I can see how someone might want to acquire a gun via a face-to-face private transaction in order to avoid any formal record of ownership.