Despite all the promise of other power sources, they still cannot effectively compete with oil. Until it does, it doesn't. It will prove it's worth as an idea when it can compete. Of course, much of the shift to gas guzzlers wasn't so much an abandonment of efficiency for its own sake. People gave up one feature to gain another.
Safety is one reason larger vehicles are more preferable to families than smaller ones.
Any family with more than 3 children cannot even fit into the smaller vehicles that get better mileage. Even smaller families might like to have some hope of their family surviving a collision which is so much less likely in the lightweight vehicles that get such good mileage. But, it certainly doesn't stop there. The emphasis on safety has meant great technological advances in improving the crash performance of smaller cars, and the more expensive makes enjoy these advances, and so the progression continues. Relying on the marketplace does not exclude exploring alternatives.