I don't mean that Apple (or Google) can't legally do it, they obviously could. The legal complication I'm referring to is the patchwork of laws regarding their customers' use of mobile devices while driving.

Android Auto running on Android is different -- it has a 50 state legal purpose: Android is a popular OS for in-car infotainment. Apple CarPlay runs on Android too, that's how it was implemented in my car from the factory.

iOS, by contrast, is not used for car infotainment systems, only Apple's mobile devices. Apple is unlikely to go out of their way to make a product for their mobile devices that is intended to be used while driving that could only be used on a mobile device.