[jdmichal]

To answer the question, I would stop phrasing it in terms of jobs and instead in terms of productivity and imports / exports. These small communities require a good amount of imports, especially if they want something resembling a modern life with modern technology. They thereby need balancing exports to pay for them. There is very little opportunity for these people to do productive work and export it. So instead there is a reliance on government subsidy for the required imports.

This equation isn't typically true for urban areas, so there's no reason for people to move. (See Detroit for details on exceptions.)