In order to get people to buy a new radio, there has to be something on it they can't get on their old radio. With the exception of the NPR stations, this simply has not happened with HD. There is nothing on commercial HD that is not found on peoples iPods.
That assumes people have the ability to load songs on their iPods that they've never heard before. I don't think they do. Most markets have HD channels that offer programming not available on the main channels, and not already loaded in their iPods. The question is: Do they want to listen to music they wouldn't buy?
I disagree with your premise. I didn't have to buy an HDTV. I could have stayed with my old tube TV and used an adapter. But I didn't. I bought an HDTV because the device was different, not the content.
Satellite (read: Sirius) decided it needed to be nothing more than a commercial-free Clear Channel. Once again, nothing you can't hear on an iPod.
Sirius offers lots of live sports that's not on an iPod. Lots of news and information not on an iPod. Howard Stern and Oprah, neither of which are on my iPod. Lots of music features not on iPod. On and on. But even with all that unique content, it's not enough to get people to buy their radios. Most of their subscribers are listening to them via their car radios, not their exclusive portables.
Large parts of local radio were destroyed in favor of remote-controlled jukeboxes. OOPS! That niche is already occupied by the iPod.
That's really not true either. Only a few formats are jukeboxes. The majority are live and local. And then you have news, sports, and talk.
Until radio delivers programming that can't be had elsewhere, it continues to be an also-ran in an increasingly crowded media universe.
We've had this conversation before, and the only programming not available elsewhere is the kind of programming that only a very small minority wants. If mass audiences wanted it, it would be on the radio already. There isn't a single mass appeal form of programming you can name that's not already available in some way.