It appears you have not done much driving on two lane highways behind big trucks that do go slow. They are a huge safety hazard.
Back in the day when big trucks were under powered it was common for them to shift down to speeds of 40 mph on a steep incline. This made passing very difficult, especially if there was plenty of oncoming traffic.
Several years ago I talked to a state trooper about speeding tickets, and was told they let truckers exceed the speed limit going down a hill so they can make it up the next. The reason was safety, just like I described above.
And many trucks are hauling time sensitive loads, like UPS, FedEx, and USPS where the shipments are to be on time. Your huge reduction in speed would greatly affect this.
AI is not yet perfected to be safe for any self driving vehicle. The time may come, but it’s not now.
Good points, except an AI truck driver never needs to sleep. On a 1,000 mile trip, a slower AI truck might arrive about the same time.