And the tax income from sparse, sprawling suburbs, is not enough to cover the cost of providing sewage/electric/gas/garbage collection/firefighting/road maintenance. So either 'wealthy' suburbanites end up being subsidised by taxes from dense 'poor' inner city taxpayers, or the city has to approve a new suburb to get a chunk of income from new house sales and taxpayers to pay for the maintenance of the previous suburb's roads, in an unsustainable pyramid scheme where the city has to build more roads forever just to stand still.