FWIW, my Moto Droid did this in 2009 on Android 2.0. But Google has to make a big ordeal about reinventing the wheel to keep the news cycle focused on them.
The big deal is that this is potentially available to everyone(who has a compatible phone) and not just a feature available from a specific manufacturer.
Why not advertise it if it's Google wants people to know now exist and want them to use?
Sure, but as you can see, at least five years ago, they had an app that was basically Android Auto running on your phone, and now they have it again, with more distracting colors and animations.