Why not take baby steps towards full automation? The reasoning, attributed to Larry Page, is simple: The more a car is partially automated, the less vigilant the driver becomes. When an exception arises, when the partial automation needs help, the driver might not come to the machine’s rescue fast and well enough. Since a partially automated car will only “reach out” under extraordinary circumstances, the resulting damage to the car, the driver, and — least of all, but it’s still a consideration — the reputation of the car maker will be concomitantly extraordinary.
The SD Cars Gold Rush Winner
Jean-Louis Gassée

This makes a ton of sense, and I’ve wondered often why companies going the incremental route think humans who aren’t mentally and physically engaged can react in time under those conditions when they already aren’t up to the task when performing as fully engaged active drivers.