What that says to me is that the problem isn't the format, but rather the device.
For the most part, radio formats are about music. Radio companies don't make music. Record companies and musicians do. Ask musicians if they think music will stay the same in 20 years. If some currently unknown genre of music becomes popular, it'll get played on the radio.
I think AM owners are dealing with that. They're not going to attract audiences in the conventional ways, so unless they can get an FM translator, they will have to find other uses for their frequencies. That may mean targeted information services, or perhaps using AM the way we once used SCA services. There are also a lot of people who are not "technology-based" people. And as I've often said, the one device that is older than the radio is the phone.
I think it's a chicken-and-egg situation. Yes, it's the device, but radio in general is not putting the effort into HD channels sufficient to motivate consumers to buy the device.