Since cars typically drive on state funded highways it would make sense to package car inspections along with the "you better set your state drinking age to 21 or you'll lose all highway funding" bill.
I don't necessarily disagree. It is pretty wild if you think about how unregulated a vehicle is after the manufacturer hands it to the customer, but that's not how -most- states operate. I guess you could just focus on states that are higher population density and hope it just rolls downhill. However, a lot of people game the system by just registering in different states or counties...it's not new at all. That is very popular with plate fees, even in liberal states like California that use certain counties to avoid higher plate fees.