Here is an article from The Washington Post about HD Radio. The HD radio boosters at iBiquity keep saying the same thing--it's the auto dealers and satellite radio (XM and Sirius) services fault. Sure it is.
There are really only a few parts to this issue: technology, programming, portability and on-demand content. HD Radio is getting aced out on all of these by competing products and services--no matter how much branding, marketing and advertising stations do. And generally, public radio stations are not inclined to do excessive self promotion. Colorado Public Radio seems to be the exception in Colorado.
Radio stations--commercial and non-commercial--that offer truly alternative programming may succeed in winning over listeners who care less about portability or on-demand content--that is, if they own HD radios for both their car and their home (portable HD radios are not common). But producing compelling programming requires creativity--and cash. Most public radio stations are not flush with either. Even fewer are flush with both. And what does iBiquity recommend? More HD radio promotion by stations? How innovative!