A possible reason...

Do high VMTs indicate the ruralness of a state?

For example I stay in a pretty rural area (out in the sticks) and have to commute to London pretty much every other week. This is because there's just not that many shops, restaurants and things to do in the area where I live. Commuting to work is easy though.

If you live in the suburbs of a large city you spend a lot of time in traffic - so high hours in vehicle, low actual miles travelled. OTOH if you live in a rural area with low traffic - relatively more miles travelled for each hour spent in a vehicle.

It seems sensible that a large number of miles travelled implies low traffic (because everyone has the same number of hours per day). Low traffic, high miles indicates rural areas? which would have lower gsp/cap values.

Thus if the price of oil rises dramatically - it would tax rural areas more than urban areas - and the price of land in rural areas should fall. This seems contrary to what some economists are predicting!

Well, that was the original idea, but supposedly the population density variable would capture that effect...