Riddle me this, a car that can't be sold or imported to a country can be driven in.. so why aren't more rare European or Asian cars getting in this way?

It's not often, but it's not unheard of, to see a Mexican Chevy in San Diego. They are small, and probably unable to pass the crash tests required to be sold in the USA.

If all they have to do is drive over the border, why aren't Porsche, Ferrari, and rare Nissan's getting in this way?