Maybe Apple doesn't want to pursue a dream which, as far as we know, can only have a limited outcome? They don't really like such compromises in products. Check this:
> Waymo’s CEO, John Krafcik, has admitted that a self-driving car that can drive in any condition, on any road, without ever needing a human to take control—usually called a “level five” autonomous vehicle—will basically never exist. At the Wall Street Journal’s D.Live conference, Krafcik said that “autonomy will always have constraints.” It will take decades for self-driving cars to become common on roads. Even then, they will not be able to drive at certain times of the year or in all weather conditions. In short, sensors on autonomous vehicles don’t work well in snow or rain—and that may never change.
https://medium.com/s/story/self-driving-cars-will-always-be-...
> Waymo’s CEO, John Krafcik, has admitted that a self-driving car that can drive in any condition, on any road, without ever needing a human to take control—usually called a “level five” autonomous vehicle—will basically never exist. At the Wall Street Journal’s D.Live conference, Krafcik said that “autonomy will always have constraints.” It will take decades for self-driving cars to become common on roads. Even then, they will not be able to drive at certain times of the year or in all weather conditions. In short, sensors on autonomous vehicles don’t work well in snow or rain—and that may never change.
Or read https://www.spectator.co.uk/2018/07/the-dream-of-driverless-... or any number of "sobering up" articles from last year.