Even the government can't be stupid enough to believe that counterfeiters are going to fill out the warranty card on their printers.
I would imagine this is an aid in proving guilt after the perpetrator is caught.
This is really meant for casual counterfeiters. There was a case in Germany where some guy ran a bunch of Deutsche Marks off his company's color copier. They got him.
"Seems to me that you could avoid registering the warranty and remain anonymous."
"Even the government can't be stupid enough to believe that counterfeiters are going to fill out the warranty card on their printers."
Printers high end enough to be used by counterfeiters don't have warranty cards. There aren't that many made. The manufacturers know where each one is.