Maintainance?
The modern car comes with lots of electronic sensors and toys. After a couple of years in the very hostile (to electronics) environment of 'under the bonnet' - they start to irritatingly fail and glitch. Quite a lot seem to go 'tilt' - game over - and leave you stranded at the roadside. Now go to your friendly local garage to get it fixed at an exorbitant price. Will it get fixed properly? Do you really trust the grease monkey with delicate electronics?
So now make the car drive itself....
1 Do you trust that all the lines of code have been adequately tested?
2 Do you trust the error recovery vectors in the code?
3 Do you trust all the wiring, sensors & interconnections?
4 Has it been hacked?
Airlines use fly-by-wire & autoland etc, and that's just fine because the maintenance schedules are such that they get inspected on a regular basis by people who know what they're doing AND you have the flight crew monitoring.
I see us getting railroaded into having the automated cars on the road, but I don't expect them to be safe until sometime next century......