Carmakers will reduce the mortality rate from motor vehicle accidents to almost zero (with full autonomy), using the collected data.
There were 37,133 MV deaths in the USA in 2017 (more than 0.01% of the population) according to Wiki.
But car makers will also get full GPS traces - showing where you live, where you work, where you shop and every time you speed. And they'll probably get what phone was seen on bluetooth, how many seats were occupied, and what radio station was listened to. All identifiable by vehicle, and very close to identifiable by driver.
Will they manage to make good use of the former, while avoiding the temptation to monetise the latter?
Of course, Google gets a bunch of data from Android users already, so one might very well argue most users aren't concerned about such things.
Maybe.
But what else are they using that data for?