While you are right in principle, I'm not sure if the downtime argument holds: Breaks of the driver are not paid currently. The car lifetime is probably not set

While you are right in principle, I'm not sure if the downtime argument holds: Breaks of the driver are not paid currently. The car lifetime is probably not set by age, but total miles driven. Self-driving cars might be more expensive, too, in maintenance (more things that can break) and initial cost. So I'm not sure how much they can gain.