Self-driving is a win for corporations in that it saves them money in the long run, and it would offer higher throughput as the trucks could run 24/7 with no need for breaks. Refueling could happen while they're being loaded/unloaded by warehouse personnel, as could general maintenance such as changing tires etc. so you would have a small fleet of truck operating nearly continuously which would be a huge economic win for these companies.
But why isn't more money spent trying to change the transportation sector? Why are trucks running across the US instead of high-capacity trains? One train could easily swallow 50 trucks worth of goods if the infrastructure was built to accommodate it. Why are things shipped so far instead of produced and sold more locally? There's capacity to produce food much closer to where people live, so 'fresh' actually means fresh, and it travels at most double-digit miles before it hits the store instead of quadruple-digit miles or more.
By all means push for self-driving, but for the environment we need to push for no driving.