It's part of this whole thing which is a rabbit hole unto itself:

https://www.reddit.com/r/explainlikeimfive/comments/6c5e97/e...

tldr version: There were very large subsidies paid to expand broadband as well as the Universal Service Fund. The companies actually built out broadband lines to a lot of areas with minimal coverage and then didn't build the last mile because it was expensive and provided "separate but equal" services such as WiMax, UVerse, or other less equitable services.