The challenge with going big is that the risks and costs raise substantially, while the price of having a local expert to manage both the drive and any eventualities (ie a human driver), isn't changing much...
Long-haul routes are important, and shaving minutes off deliveries is a big deal. Improved driver logistics and routing are probably wildly more profitable than automation (and risks of highly visible automation failures).
After all some trucking companies can sometimes even get away with not paying their drivers because the drivers didn't drive enough miles to cover the truck lease this week and therefore go home with a bill rather than a paycheck.
Long-haul routes are important, and shaving minutes off deliveries is a big deal. Improved driver logistics and routing are probably wildly more profitable than automation (and risks of highly visible automation failures).