Then anybody could see stolen vehicles and report them. That would discourage theft.
Then anybody could see stolen vehicles and report them. That would discourage theft.
Sometimes VIP type people get deputized or have their vehicles somehow associated with a police agency.
Most likely the first thing thieves do is switch their plate with the plate of a similar car (same make, same color), then drive to another country where they'll be resold.
A professional car thief who steals cars in order to resell them may very well work that way. But I suspect those people are a small minority in comparison to the opportunists who probably don't have appropriate spare plates on hand, or the desperate criminals trying to pick up a getaway car, or the joyriders, etc.
In another car that I'd just purchased a cop pulled up next to me at a light and asked about my lack of plate. Said I bought it a couple days ago, he said I have X days in this state to get tagged and drove off.