It's a chicken and egg situation: the radio stations say no one is listening so they neglect their subchannels, but no one is listening because the radio stations don't give a good flying flip about making sure the content is worth listening to. No one is going to buy a radio that doesn't give them what they want to hear, and no radio station is going to install HD and program alternative content without the radio base to justify it.
So that leaves us in this suspended state of almost giving a damn but not enough to do anything interesting. Someone needs to pull a trigger: either make the subchannels compelling and make sure they're working 24/7, or turn all the HD off and be done with it. Either way SOMETHING will be done, so us bunch of radio geeks can stop arguing in circles.