Even if there's good reason to use it, there's no potential for growth. The only way this can go is down. It's pretty much going to be a race to recoup the investment before all these rural areas are covered by cellular (even 2G would be faster than dialup!) or satellite internet becomes cheap enough.
Yes; Verizon has an offering designed explicitly for rural areas[1], but it's expensive. The linked article is from 2012, and prices have since declined, but the general gist of the service is the same: a big antenna you bolt to your house or a tree and will pull from an existing account-level share plan (if you have one).
People will have better luck with rural telephone companies trying to stay alive then big wireless carriers. Sprint and T-Mobile absolutely suck in coverage area for rural folks.
One example, Steele ND and the surrounding area is served by a small rural telephone company that is laying a lot of fibre (I'm hoping they head North). A 200M plan (no cap) for $45 a month. This is being repeated quite a lot in rural areas with rural cooperatives.
I usually think of where I live as rural due to the distance to a major city (20 miles to Athens, GA), but I do get occasional 4G inside the grocery store. It's more exurban than rural.
The last time I lived in a deep rural area (Norton, KS) there wasn't a good cell option. The cell tower that covered the town was flaky at best in terms of reception. So, I guess your mileage may vary applies in that situation?
If Verizon is trying to expand their wireless offerings into areas where dial-up is currently the only option, then having much more direct marketing access to those dial-up users sounds pretty useful for them.
Yes, an anecdotal example is my parents. They live 45 minutes outside of Columbus, OH and have a Verizon 4G adapter for their desktop. In fact some of the smaller carriers have poor cell/data coverage where they are.
Economics of covering the area. If it costs more to cover than they expect to make in any reasonable time frame, especially if it never breaks even when you account in maintenance, then they won't do it.
[1] http://www.psmag.com/nature-and-technology/neighbors-still-u...