Online shopping require fast delivery. From hub to receiver, it still takes a long time for a package to travel, especially in a big city. This trip in town consumes a lot of time, labor, energy and traffic space. We call this the "last-mile" dilemma.
The last-mile trip consists of many transfers. Post vehicles have to stop at a post office/station to unload and reload.
This is a structural reason of time wasting.
With help of autonomous driving technology, vehicles don't have to park only in order to transfer contents. It is much faster to dock to each other and transfer contents on the road.
Robots drives better than humans. They can easily dock two cars and save us trouble.