2. Attention. How does a car ensure that its driver re-engages when required? Imagine what would happen if thirty or fifty cars pull over because their drivers are busy finishing emails.
2A. If self-driving cars become common on a given highway, how do they cope with griefers? (Other drivers who manipulate the software into giving up, or worse.)
7. Having remote drivers is about as expensive as having an on-board driver.
9. Safety. Self driving software is not infallible, and there are other vehicles on the highway, and unusual situations can develop.
9A. Kinetic energy. Major accidents at highway speeds can be lethal.
10. Publicity. Accidents on highways can also be spectacular/photogenic.
11. Liability risk. Anything that can be blamed on the software, will be.