I see at least four big problems with having drivers that sit around to supervise the AI.

• It’s a mind-numbing boring task. How does one stay alert when most of the stimulus is gone? It’s like a real-life version of Desert Bus, the worst video game ever.
• Human skills will deteriorate with lack of practice. Drivers won’t have an intuitive sense for how the truck behaves, and when called upon to intervene, they will probably respond late or overreact. Even worse, the AI will call on the human to intervene only for the most complex and dangerous situations. That was a major contributing factor to the crash of Air France 447: the junior pilots were so used to pushing buttons, they had no stick-handling skills for when the automation shut off, and no intuition to help them diagnose why they were losing altitude. We would like to have Captain Sullys everywhere, but AI will lead to the opposite.
• The AI will shut off before an impending accident just to transfer the blame onto the human. The human is there to serve as the “moral crumple zone” to absolve the AI of liability. That sounds like a terrible thing for society.
• With a fleet of inexperienced drivers, if an event such as a snowstorm deactivates AI on a lot of trucks, the chaos would be worse than it is today.