I recently purchased a Sangean HDR-141 compact HD Radio receiver after the local station that broadcasts baseball decided to move their AM/MW2 station (and most of their FM stations) exclusively to digital HD Radio broadcasts. In their announcement, they established that the time was right now that 20% of their audience was equipped to listen. That’s… an astonishingly low percentage, especially given that the technology was approved as the U.S. digital radio broadcast format over fifteen years ago. I, myself, was able to find one acquaintance capable of receiving HD Radio (in their car), and this receiver only handled FM.
Adoption has seemingly been low in the other direction as well. Though the airwaves near me seem flooded with broadcasts, the only HD Radio content is coming from the aforementioned station. Part of this is almost certainly because the standard itself is patent-encumbered bullshit from iBiquity3 instead of an open standard. Transmitting requires not only the encoder, but licensing fees directly to iBiquity. The public-facing language is very vague on the HD Radio website, but receivers also need to license the tech and I imagine if this was free they’d make a point of it (and there’d be more than three portable HD Radio receivers on the market).