If it's a feature required by the government to be road legal, it's likely not run and/or pass emissions testing if it's not working. And it's a point of failure written by people who are bad at software.

Alternatively, computer control of real world systems (e.g. acceleration and braking) can lead to actual accidents, totaling the vehicle. There was that lady who claims her Tesla's software caused a crash, and, without commenting on if that is true, it's plausible.