It's not so much about accountability in the legal sense, it's in the public perception sense. "Old Uncle Bob forgot his glasses again and ran over a kid" does

It's not so much about accountability in the legal sense, it's in the public perception sense. "Old Uncle Bob forgot his glasses again and ran over a kid" doesn't have any implication regarding my use of a car. "A self-driving Tesla was confused by work signage and ran over a kid" would destroy a lot of trust into self-driving cars.