Looking at the Tesla video, a human will see the obstruction way in advance and will see other vehicles going around it. The sensors on a car may not be sufficiently long ranged to safely stop. Now apply that to an 80,000 lb load -- no one wants to be in the way of that. A 4,000 lb vehicle is 5% of the truck+load weight -- it goes through a heavy auto like it's not there.
I would think installing embedded sensors in the interstate system and major trucking routes would be economically feasible. Driverless trucks hauling goods between hubs then having human drivers navigate the local roads seems like a good use of the technology.
There is almost 50,000 miles of Interstate highways in the USA. Installing a sensor system would take years, possibly decades, and as mentioned above, by the time it was complete the first segments would require updating. Then there's construction -- interstates are heavily used and under repair constantly. Segments would get interrupted and human error would certainly cause problems.
That's technical stuff. Let's consider logistics.
If the truck stops for any reason (e.g., missing or damaged sensor segment), the company has to get a driver to that location, requiring 2 people (someone has to drive the driver). Lost time and increased expense.
To start a drive, a driver must drive the truck to the interstate, and must be followed by a second vehicle + its driver to take him back. At the other end the process is reversed, again requiring a second vehicle and 2 people. Depending on distance from the origin to the Interstate, and the Interstate to the destination, the personnel cost may be greater than just paying a driver.
Building distribution hubs near the Interstates is a good idea, but there are tens of thousands of trucking companies in the USA that do long distance hauling. Getting them to cooperate and add on the expense of using someone else's hub to cut out drivers? That's a hard "no". Getting the government to mandate anything won't happen -- the trucking industry has a LOT of political pull at the states and Federal level, so passing legislation they opposed will not happen easily, if at all.
The trucks needs refueling, which will require a driver. This can be scheduled, but requires planning. Can fuel stations be built specifically for this? Sure ... but the land in necessary locations may not be available or expensive, pushing up costs.
If there is an accident and the truck is re-routed? Again, it requires a driver, and the lost of time and cost of manpower to get a driver to the truck is a problem.
Self-driving trucks on a local scale may make sense in some areas, but it's still a complex problem. Doing it on large scale is a logistical nightmare.