I found this link and started reading. It’s dated back to 02, but
argues a clear point why HD radio’s haven’t been selling and addresses
the issues surrounding jamming of competing weaker analog signals.
http://www.indybay.org/newsitems/2002/03/12/1183311.php

The National Association of Broadcasters (NAB) is pressuring the
Federal Communication Commission (FCC) to force acceptance of new
version of Digital Audio Broadcasting, a kind of "Fax For Audio" on to
the existing AM and FM broadcast bands. To accomplish this, the NAB
plans to double the amount of space on the dial that a station uses,
thus jamming the signals of weaker stations next to them on the dial.

The all-digital imposition on FM and AM bands contrasts to the rest of
the world, which establishes DAB on a third band. Historically in
America FM was placed on a different band from AM rather than
obliterating it.

Other than loss of diversity, there are many other issues to face if
analog radio is forced out of business by special interests.

Maxwell asks, "Over one in five Americans find the only radio station
that speaks to their soul are the noncommercial stations that are
often inevitably the weakest and most distant one on the dial. Besides
losing your favorite programming, do you have hundreds of dollars to
replace every Walkman, clock radio, car radio, home stereo, and
boombox? Is your locality ready for all your old radios going to the
landfill? Or the pollution caused by manufacturing to replace
500,000,000 radios in America alone?"

The Europeans and Canadians began their push to establish Digital
Audio Broadcasting (DAB) in 1992 with a third band. But the new DAB
signals offered an insignificant increase in quality, according to
Sony Inc., during testimony to the FCC. Combined with the same bland
programming, the European and Canadian DAB flopped in the
marketplace.

So the coalition wanting to go all-digital had to figure out how to
force us to make the conversion, without a third band that might fail.
The typical listener is happy with the current signal quality, and
really wants more variety, and fewer ads. Proof of that is the
flourishing ad-free Internet and satellite radio stations, and
declining listenership for traditional stations.

Instead of honest competition, they decided they would make the
government compel all broadcasters to convert to digital on the
existing AM and FM bands.

Radio stations will be forced to double their bandwidth on the radio
dial. This would be a "big box" store effect, destroying the smaller
and weaker competitors and further homogenizing the airwaves