I think this is part of it, "iPhones are cool, and this is like a giant iPhone!", but I think a larger part of it is that it's easier to design/program for and

I think this is part of it, "iPhones are cool, and this is like a giant iPhone!", but I think a larger part of it is that it's easier to design/program for and actually possible to update after the fact if that's required. There's probably something here for using the same parts across a whole line of cars, too vs testing and fitting buttons.