Stolen cars are often sold for low amounts of money - like $50 - and then used to commit crimes that are not traceable from their plates. It hasn't really been possible to steal and resell a car in the United States for many years, barring a few carefully watched loopholes (Vermont out-of-state registrations is one example that was recently closed).
When Kia and Hyundai were recently selling models without real keys or ignition interlocks, that was the main thing folks did when they stole them.