Sprint not improving their network in smaller communities is not true. I live in small town with a population less than 45,000, all four major carriers are located here and almost on a regular basis I see tower crews doing upgrades for Sprint and Verizon.
Verizon has been busy adding AWS and even erected a few new monopole cell sites, Sprint has been busy adding Band 41 2500MHz (NSN mini macs and 8T8R) to all their existing 800/1900MHz sites, cell site optimization, replacing 1900 RRUs, and even adding 4x MIMO PCS upgrades here.