A Tablet as a Replacement for, Not Addition to, a Car Display

Apparently Apple is in talks to do... something in along that line. It has had some niche successes with having auto makers use tablets instead of a proprietary in-car entertainment system. In past years the profit margins for entertainment and navigation systems would have made it difficult to convince auto makers to fully integrate with a third party device, but now... if you pay $2500 for in-car entertainment or navigation, or even $1,500, even if you don't feel like a chump it's difficult to imagine that you've viewed in any other manner by the car dealership.

So why not become, in essence, a large tablet retailer? Have the device fully integrate into the vehicle, seamlessly controlling navigation, entertainment, climate control, and the like? Sure, you have to somehow control for people watching movies while they drive....