Might be a 1900 MHz LTE area, in which case you need a specific phone. http://www.t-mobile.com/optional-services/coverage-phones-1900.html
I saw this TracFone ad on here among the random ads and found it somewhat interesting:
It doesn't outright say that they support 4G LTE devices, but they chose to picture one in the ad.
^^^^ We have a winner! It is an unnatural obsession from the data curmudgeons.
It's that simple.
And yes, overall tethering and roaming are niche products relative to the basic service that people want.