How do you judge quality? Anecdotal evidence? Government studies? Guessing? How do you account for bandwidth, reliability and coverage in the specific nooks you happen to go in? How do you account for/plan for coverage while traveling?
Price, obviously, is easy to discriminate on... except how do you determine your current, and predict your future, needs on three axes (text, voice and data)? And do you determine your needs and figure out what the cheapest is, or a more complex MxN matrix?
Are customers all on month-to-month where you are? They seem to be mostly accepting 2-year deals where I am.
Most importantly, there are tons of ways to incentivize switching without offering deals to all. Free phones if you bring in a phone offered by a rival, etc. Therefore, companies can compete over hopefully cheap differentiators and not on price or expensive infrastructure.