Because you drive your car all over the country. Your job is down the street. Let state government regulate that.
oh I see where you're coming from. I disagree with it, but ok -
Excuse me, but the states have the right, and the authority, to regulate anything within their state. The feds need to keep their noses out of the states and go back to doing what the constitution allows them to do, which is national defense etc. Keep the feds out of my hair and I will be much happier.
(and no.. i have no source to back it up... i had heard it about 10 years ago)