I love this idea. It makes a lot of sense - especially in communities with elderly people who can't get to shops easily on short notice.
However I am concerned about theft and vandalism. While some cities may have an ethos of these things being left alone, I can see them being tipped over quite often in some areas. There's also the danger of smashing the top and stealing what's inside.
I imagine these are fairly well tracked though, so no one is going to steal an entire robot, but damaging them seems almost inevitable.