The deal with HD Radio in new cars is this: At the current rate people are hanging onto the cars they have, it'll be 11 years before most people are driving what are now contemporary cars. So, even if every one of them had HD radio, it'd be more than a decade before "everyone" had it in their cars. For the most part, the guys at the dealerships don't understand and don't explain HD radio. Each manufacturer's HD setup is different. Some allow you to access HD-2 and HD-3 by just turning the tuning knob or pressing "seek" once the HD signal locks in. Others require you to press a "multicast" button. Still others require you to press in the tuning knob, which opens up a menu of secondary and tertiary channels.
In other words, the average driver will have to read the owner's manual to understand how to listen to HD. And we all know nobody reads the owner's manual.