I thought it was to give the returning GIs the opportunity to fulfill the American Dream, i.e. detached house and a car. If you go out of the east coast cities into the midwest, you'll find that most people, when they get the money, build 1500 square foot houses on quarter acre lots. That's pretty much been a standard since the beginning of the country: That's how New England was built in colonial times and that's how Mound City Missouri was built, for example.

One other point is that as America grew there was a lot of open space. So people who wanted to stay in the east coast cities did so and the ones who wanted out of the cities moved west. That's still an option--there are huge, huge, huge tracts of undeveloped land throughout the western part of this country. And a big chunk of the country where the population is declining. In fact, there is consideration of gradually building a new "Buffalo Commons" national park that would cover around 1,000,000 square kilometers. (Estimated based on 5 * area of South Dakota.)
http://en.wikipedia.org/wiki/Buffalo_Commons

Interesting gardening observation: If you go to a garden shop in the high parts of Idaho, Colorado, Utah, etc. you'll find that lots of the plant varieties are "Siberian" this or that--because the climate of the high prarie in the U.S. is comparable to parts of rural Russia. It's ironic that there are many people in America who dream of retiring to Montana but so very few people in Europe who voluntarily choose to live in the Krasnoyarsk Krai.