Huh? 80-90% More like 99.x%. Modern cars are extremely reliable, and even if they do fail (usually due to poor maintenance), that rarely causes a crash, since a disabled car can easily pull over to the side of the road, unlike aircraft.

Almost all crashes are ultimately caused by driver error. Doing FAA/NTSB-style investigation on them would be pointless, because that's exactly what they'd find: people were driving recklessly, inattentively, etc. And there's nothing that can be done about that, because we as a society absolutely refuse to have serious driver training and any standards for driver conduct. We can't even agree on whether the left lane is for passing or not! Try driving in Germany sometime and you'll find that what we accept from drivers here in the US is really quite awful.

To be fair, probably 80-90% of NTSB aviation investigations final reports contain the words “pilot error”.

The term "pilot error" is outdated, and suggests blame. "Human performance factors" is usual way to describe such mishaps.