My impression is that Uber simply can't afford to not be the absolute first in driverless taxis. They're burning money to stay in the taxi business. Their entire business model relies on keeping the price somewhere in the range of what it is now and not paying a driver.
It might be that the marginal advantage of not having a driver on the highway section of truck delivery is not large enough to justify building out a trucking network. They'd have to establish relationships, buy trucks, service the trucks etc. all of that would be time and money that isn't going into their big bet.
It might be that the marginal advantage of not having a driver on the highway section of truck delivery is not large enough to justify building out a trucking network. They'd have to establish relationships, buy trucks, service the trucks etc. all of that would be time and money that isn't going into their big bet.