Isn't there an economic reason, to do with amount of revenue generated, versus cost of provision? It makes business sense to plant cell phone network masts ("towers" in USA) in areas of high population, and (often forgotten) provide network infrastructure to service them, (fibre links, routers, etc), and crucially, power. Less so in remote rural areas. You don't build a railroad or freeway to every little village or hamlet. If it would take 100 years to get, in usage charges and revenue from selling plans, to pay back the cost, ain't gonna happen.