86% of U.S. has Home Density of 15 Homes or Fewer Per Plant Mile

Rural fixed network plant is expensive, on a per-location basis. Most of the land surface of the United States consists of areas where a mile of fixed network plan passes no more than 15 homes, for example. 

In the United States, areas with linear plant density of 15 homes or fewer represent nearly 86 percent of the area of the lower 48 states, yet contain just  12 percent of the locations.

source: CQA 

That is one reason why U.S. fixed networks often take so long to build. Earning a profit from investments in new plant is difficult, most places.