Cost - as others are pointing out, it costs a lot more (in time and money) to design a physical interface, and then you can't deliver updates if there is an error, so you gotta really take the time to test that everything works.
The other is that, when it comes down to it, consumers probably care more about other things, like price, MPG/range, exterior styling, brand loyalty, etc. This means that even if the car has a sub-optimal UX, customers will still buy it (because the positives outweigh the negatives).
The other is that, when it comes down to it, consumers probably care more about other things, like price, MPG/range, exterior styling, brand loyalty, etc. This means that even if the car has a sub-optimal UX, customers will still buy it (because the positives outweigh the negatives).