you forgot that auto pilot likely is only used or only works under certain conditions. So that 1.2B miles is selective. You can't extrapolate that to the 10-20 deaths, which I assume you calculated from ALL miles driven
Granted, I am approaching this from the perspective of a more relaxing driving experience not necessarily from a pure safety standpoint. People spend 20,000+ hours driving in a lifetime making that less stressful is a huge benefit even if they are still stuck in their cars and can't get work done.