I should have been more diligent by including suburbs in my comment. Furthermore, you're very right that the water and sewage is even more important than roads, and that overbuilding happens in the suburbs. But you may also have an overly optimistic picture of rural areas, because I can think of quite a few four lane highways where I grew up that go out into relative nowhere, and do so at huge cost. There's a town of 20k people there that has a beltway!