Every new development should be able to sustain itself by providing a town center, schools, libraries, markets, jobs, and other civic/commercial activities within safe walking distance of every home.
If a development cannot sustain itself, then residents are forced to drive outside of their community to meet their needs, which puts more cars on the road (increasing danger to both people and the environment) and forces those that cannot drive to rely on others.
Our children and the elderly as well as others that can't or chose not to drive suffer in these single-use developments.
The role of our government is to develop a healthy infrastructure for its citizens. Requiring mixed-use developments with their own city centers would achieve this goal.