To quote a popular expression "it wasn't ready for prime time". BMW offered HD in their cars but suffered major warranty losses when buyers kept bringing their cars back because "the radio doesn't work".
No, that is not true. An ambulance-chasing law firm either looked into or actually sued BMW in a class action. This action was based on a couple of reports and a lot of garbage from some HD-hating folks.
I asked the service managers at the two BMW dealers I go to, one of them a top-10 dealer nationally. Both said that they had never had such complaints.
I have or have had 4 BMWs with HD in them, and the radios work fine, and the HD works very well, particularly on AM in noisy metro areas.
Intrinsic technical failures (insufficient range and loss of lock primarily) meant that, while the HD sound quality was good the signal wasn't reliable and unfortunately the problem is in the technology and not the individual radio units.
Again, using my car HD radios as examples, in areas outside metro LA, such as Redlands, San Bernardino or Oceanside, where the KFI and KNX analog signals are beginning to be noisy, the HD signal is fully locked and clear and interference free. On FM, I've carried Phoenix FMs like KNIX and KMLE almost to Quartsite on HD.
Whether there is an economic reason to have HD is different... and I believe that for AM it's a non-productive effort.
AM is fading, and irrelevant to most Americans. And in the top 100 metro areas, the average is less than 2 viable AM facilities per market, so most stations can't benefit from HD because they are horrible facilities anyway.
On FM, the real benefit other than FM translators is in the HD2 and HD3 channels. While commercial FMs have been stopped from making any significant contribution on Hd due to the recession, the NPR stations are examples of providing valuable new services on HD channels.