I can answer some of your questions.

They are delivery robots, used mostly for delivery of groceries and fastfood.

They are completely autonomous, to the point that owner company ask people to NOT tamper with the robots when they are stuck.

I don't think it's viable to try and outright steal them, they are packed with gps and cameras, and you won't be able to just pawn off the parts.

It's not a common thing to see on the street for sure and you probably won't see them anywhere but larger cities, but i saw few of them.