What are the good reasons to develop an area? Proximity to a better one? Fresh water sources? Desirable weather? Good schools? Unpolluted environment? Nice parks?
All of these things. The more the better, and places with better potential get developed first. Commercial opportunities tend to be developed first, followed by better weather. As all these places got developed, tertiary concerns become more important. Rural America will mostly stay rural and suburbs will slowly develop economies and become part of the metro areas they surround.
Suburbs are a Ponzi scheme. They do not cover their existing infrastructure maintenance costs...