The problem is more so that older ideas of connectivity are still being held onto. You car's receiver is what is not keeping up. I can't imagine actually plugging my phone into my car every time I set foot in it, and haven't for several years.
I disagree with this sentiment. We are talking about cars that are less than 2 years old and at the time they were sold offered the newest technology available at the time. People are not going to swap out the head unit's in their car annually like they do a phone. Google's decision to limit USB connections to MTP limits the functionality of what is supposed to be a high end phone.
I have a 2010 vehicle with the first generation Sync with Navigation screen installed. Via USB it will index media allowing voice control..play playlist xxx, play artist xxx. It's very useful, but the Nexus won't do this. The Nexus connects just fine via Bluetooth AD2P, and streams everything wonderfully, but other than skipping to the next or previous track (also works with many third party apps, not just stock music player), you must control everything with the phone. So I'm stuck using an old iPod connected to the USB port to get the voice control I want. This sucks because I have to pull the device and sync it to my computer to update anything. It's not seamless, but it is safer to use the voice command than it is to try and tap on the Nexus screen at 70 MPH.
I understand new phones can't maintain backwards compatibility forever, but Mass Storage Mode is still widely used and is not obsolete technology. It would be great if the first version Sync could be updated to support Media Indexing via Bluetooth, but replacing the head unit every year because Google decides they want a new standard is just crazy.