Suburbs are not feasible, cost wise, from a municipal standpoint. They've been heavily subsidized by the denser parts of the municipality, and surprisingly by the rural parts too.

The cost of maintaining infrastructure in a fit state of repair (water main, sanitary sewer and treatment plants, roads, bridges, storm sewer, curbs, sidewalk, street lighting) for these semi-spread out houses is the same as maintaining it in denser areas without the benefits of the higher tax income.

Additionally, the spread out housing, at least here, has overtaken lower lying wetlands, filled in creeks, and increased water flow down the water courses that do remain, causing erosion, sedimentation, and killing off the aquatic wildlife. Ontario has just started to require Low-Impact Development, standards that require constructing artificial wetlands, soak away pits, raingardens, green roofs, or similar measures to reduce water flow off site and encourage aquifer refilling. These all cost extra money above and beyond what the cost of repair has been up to now.

I work as a consultant designing infrastructure repair and rehabilitation for municipalities, and have seen the cost of these projects. For most of them, it's the equivalent of their property tax for ~40yrs, and typically has a lifespan of 50-75yrs on the high end.

Suburbs are being subsidized through grants provided by our Federal or Provincial government, which is funded through other taxes.