bedmison

Maker-built infotainment systems are largely garbage from the user's perspective. Oddly, it seems that the Germans are particularly bad at it. In the past 5 years, I've owned VWs, Audis, Porshces, and BMWs. The BMW is by far the best, but it's still not brilliant. Adopting Ultra would be an admission that they can't do it themselves, and I would think it would limit brand differentiation, because the Apple UI would (probably) look the same regardless of the car. On top of that, the makers would have to pay for the privilege. 

The answer to all of your questions is money, and makers view the infotainment system as a potential revenue stream in the era of more connected cars. Anything that gets in the way of that will be problematic for them. Ultra would mean Apple is a mediator for the data they want to monetize.