That is a big part of it.
I think another big role is the American attitude: bigger is better. For years we have had it great with very low gas prices. Shit, I remember when I started driving it used to cost me $17 to fill the tank of my G20. What was that $1.70/gal? Now it costs me $60 to fill that same tank.
Take a look at the roads nowadays. At least here the trend is finally starting to move toward smaller cars. There are a LOT more bikes and scooters out now too. It's going to take oil prices reaching record highs for the population to change its demand from big grocery getters with 5.8L hemis, to 1.8L efficient machines.
The big companies are just looking for profit, of course. When demand says put a hemi into everything, obviously the big companies will do just that. Its sad, but it's going to take gas prices like we are facing now to get the advances in technology.
I paid $4.70/gal yesterday. That's just crazy.