They don't work everywhere all the time. They clearly exist; they're out there on the roads.
> a self-driving car can't bring the food to the door because the veteran is in a wheelchair.
It could, however, deliver the veteran to their appointment, in the many cases where the path between their home and the VA is one of the ones a self-driving car can already navigate.
Grocery delivery, by contrast, could still be done by a person, but modern logistics technology allows that person to deliver groceries for multiple people with one trip to the store.
> It can't knock on the door, have short chat, ask about the wife (who is deceased five years), and when necessary... Call elder care services when the veteran says he just talked to her yesterday.
That is an entirely different service. To see why, consider the veteran who has that problem but has never needed (or anyway requested) to have groceries delivered.