Also, all of these are much simpler problems than fully-autonomous operation of a vehicle on a regular road surrounded by other users, which involves teaching the system how to deal with an enormously long list of edge cases.

I don't envy people tasked with balancing the need for self-driving car software to be able to handle a sufficiently large number of possibilities to consider eliminating the driver with the need for it to have a small surface area and sufficient degree of tractability to be able to minimise bugs.