Sure, I have no problem with the "black box" part in my example running Android but if I don't like that bit or it's no longer the best system for the job I should be able to pull it and replace it with something I do like without having to take a hacksaw to the dashboard of my car, and without losing the integration into the handsfree microphone, heads up display, steering wheel controls etc.
This is going to become more important over time. For years stereos in cars had radio and tape or if you were lucky a CD player and that was fine. Then music changed and everyone had mp3 so there was ipod integration which generally stopped working as iOS changed. There's 3.5mm inputs but the control interface on your phone or mp3 player is crap for use in a car. There's bluetooth but support is patchy, newer stereos have better support but without a standard you're stuck with the one that came with your car.