First, both Teslas and most
First, both Teslas and most new cars already have some form of this. How do you think Tesla knew how Autopilot categorized the semi trailer in the Florida crash?
Second, just about every non-pilot I run into has an exaggerated idea of what an autopilot does. It just maintains course, altitude, and airspeed. Autopilot is a good metaphor, because airplanes that use them are not autonomous. It's a pilot aid.
Last, flight data recorders aren't there because the plane has an autopilot. They are there because airliners operate in a complex environment and, while accidents are vanishingly rare, a fair percentage of the accidents are fatal. They are also "big ticket" transportation.