But I think another factor has to do with the water table. In some places the water table rises high enough to flood basements, so you don't usually have basements at all in those places, and subsequently you don't have large reservoirs of radon adjacent to living spaces. I know of some people here in CO (where we have decaying granite in the soil) that don't have a basement and still need a radon ventilator, but it's not very common.
There's more to the south than Texas, y'know. I can't recall if radon tests are required during a home inspection here in NC, or just highly recommended, but when I was buying a house last year I toured several homes that had radon mitigation systems installed.
...but if you ever get annoyed by the whir of the fan, unplug it for a month and do an alpha-track monitor. (Or get a continuous monitor, they're cheap now!) There's every chance that simply having the cracks caulked and the piping in place, might do the trick all on its own, with no need for active depressurization.
In the south, Radon "can" be an issue, but it simply isn't an issue. In New England, it is often an issue.