All of the outlying neighborhoods where I live developed off of existing roadways (mainly rural highways between towns) that serve many people more than the ones who live along the way. Yes it is true that those subdivisions have roads and cul-de-sacs and whatever; those are built by the developer of the subdivision, and since they see only light passenger car traffic they don't require a lot of upkeep. The main roads in and out of town were already there.