Well, it's exactly the same story as we debated few weeks ago with aeroplanes.

The engine control needs to be computer controlled nowdays, there's no alternative any more. You just cannot make a fully mechanical motor that would pass any emission control tests, nada. Same goes for the power steering, non-locking brakes, traction control, parking assistant, etc... they all are computer controlled and connected to a common bus so everything plays nicely together.

As for the entertainment system, it is a selling point that customers want... so it has to be built in too. (Remember, the more gadgets you cram into the car the happier the hippy customers are...)

Now comes the cinch; it would be so much cheaper if you could also use the same bus and protocols with the entertainment system as is used by the car control computers... and even cheaper if you could further integrate systems toghether! The less number of separate boxes and separate sets of wiring you can get by with is money to the pockets of the manufacturer!

So we get to the same state as with aeroplanes: the manufacturer needs to weigh possible safety risk with sure hefty bag o' dough.

Wonder which way they will swing?