And those codes could leak, at which point we're back to the beginning.
But let's assume it doesn't leak. Is it worth it? Consider the enormous cost that would be required for this: every new iPad that is manufactured would need to be recorded in this central database. Secure access to it needs to be set up and maintained from all Apple stores around the world. Is that worth it for a rarely needed feature that most people don't care about?
If you instead try to do a secure hash of, say, the serial number, that's much less cost to maintain, but that hash will almost certainly leak. (Think DeCSS.)
