This means more places to eat, to play, and buy stuff than a rural community can offer, in an area safer and much more homogenous than the city. Throw in cable TV, two cars, plenty of debt, and a lawn for each family, and you have entire herds of people living the American Dream. Sure, they put up with mile upon congested mile of ugly strip malls, traffic lights, and sport-utes, but in the end it's better than living in the crowded city. Conversion of farmland and pristine forest to suburbs is much more democratic, more American. The government, too, is a big supporter of sprawl.
Life is easy in the suburbs.
Easy and mindless. So, the government promotes this planned insulation, and cashes in politically on the mass complacency and weakness promoted by the 'burbs. Put a left turn signal in Manhattan, and see how many people actually wait for it. The government hates that sort of spine. They'd rather a nation of lawn-care experts than writers, artists, or independent laborers.