I don't know why there are areas in US that lack service providers. Maybe someone here can explain it - I presume the reason has to do with something US specific about the business rather the overall cost since lots of low GDP areas globally can have good cellular coverage.
Jokes aside, you'd be surprised how good network coverage is in some remote areas that seemingly have very little economic value.
It's not about technical expertise but of business. Why the business does not provide the service? I have no idea.
And all distilleries and breweries, since they waste perfectly good produce to brew alcohol, and just increase our healthcare costs
And gold courses.
If you live out of town, or in a really small town, you're gonna have tougher luck