There are solutions being created to minimize the visual pollution aspect of cell phone towers through "stealth sites". The cell phone companies have had so many denials at Planning Commission hearings around the country, that they've had to get clever with how to put their towers in built out areas. So now they are disguising them as trees, putting them inside of large flagpoles, and a few other creative things. As they become better at that, I imagine there will be more hidden towers in built out areas of Jax, which of course means better service.
It is much easier to locate a cell tower in an urban area (on top of buildings), than it is in sprawling suburban developments. There is probably a strong correlation between poor cell service and suburbanization. So that is probably why Jax as a whole ranks so poorly in this category.