Supply and demand. People want to spend hours a day driving between home and work just so they can have their own little place in the burbs, where it’s nice.
Builders want to sell them houses. Farmland is the easiest to buy and build on, so that’s where the developers develop. The land is worth much more with a house on it than with wheat on it.
The only real solution is to drive gasoline prices up so high that people want to live in the cities again. But now that we have electric cars, not even that may work. We’ll have to make cities more attractive than suburbs—with culture, education, and vibrancy. We’ll have to eliminate urban poverty. That, more than anything, will make cities look attractive enough to bring the people looking for their own little bit of heaven back.
Why do people leave cities? Bad schools and fear of crime. Turn the schools into the best schools and get people good jobs and eliminate poverty, and you’ll drive crime rates down. Then, over time, people will want to come back to cities, and there won’t be any demand for those mushroom developments. All the developers will come back to the city to try to make money here.