Cheap housing materials, cheap city water pipes, cheap everything has created a nightmare for suburban communities that are failing.
Older cities have much stronger pipes (lead, usually) and are not experiencing the sorts of massive public works headaches I've heard of in some suburbs.
The system of hook up fees for utilities, designed to "encourage development" at a time that development=suburbanization was axiomatic, combined substantial direct subsidy of infrastructure for things seen as "employment centers" like industrial and office parks, with implicit cross-subsidization from more dense to less dense development.
However, when that infrastructure has to be replaced after the sprawl development has been entrenched, there is less of the denser development that is more efficient in terms of utility networks to repeat the cross subsidy ... and the entrenched institutions for subsidizing green field sprawl development don't help very much for major maintenance or rehabilitation of existing infrastructure.
The transport grid is just one grid where pockets of higher density can reduce network costs per resident. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
