[freedomben]

> So the plate is clearly for something else, mainly I think, to indicate that you've paid the appropriate registration fees on the vehicle.

I think it's so they can identify the car owner quickly and easily and hold them liable for any law violations or damage. And of courese, at least partially (or ostensibly) for revenue generation and taxation purposes (though if that's all it was for, just using the VIN would make more sense IMHO, which is why I suspect it's more for the former).