Some areas have set moritoriums on building additional cell towers.
I don't know the reasoning.

I'm 5 miles off Interstate 5, and always had bad cell coverage. I bought a TracFone and couldn't get any kind of signal. My vet's wife refers to this as 'cell hell'. So I called a couple of cell phone services and asked if they wanted to put up a cell tower in my back yard. They said they would like to, but they couldn't due to the local moritorium.

Sue