Nice chats don't have to resolve 'American tribalism' to be worthwhile.
Sure, they might be worthwhile in isolation, but the context from the GGP was that they're worthwhile enough to worry about Amazon Go (by being a valuable source of interpersonal contact during times of "increasing tribalism").
Why use a throwaway account?
But to answer your comment: the comment was not about the chit-chat with the cashier, but other people in the line.
Even if this slight increase in social interaction did anything ("cash or credit?" -- "Credit, ma'am"), that's as ridiculous as fixing race conditions with sleep() calls (hehe, race conditions).