The "shared necessity" factor also means that you regularly meet acquaintances there by accident. It just doesn't happen at the Wal-Mart or Home-Depot 15 miles away anywhere near as often as it would happen at the town general store or the local main street shopping district. Possibly because nobody actually spends time at a big box store or strip mall; they're such deeply unpleasant spaces that you basically just do what absolutely must be done and get out. So now a little extra stroll around to window shop has been replaced by extra time in the car to drive 15 miles across town in the other direction to go to some other big box store.

It's not just a small towns thing, either. The main street shopping district I had in mind just now is in the middle of Chicago. And it doesn't happen so much there, either, anymore, in the post retail apocalypse era. Now it's all bars and restaurants so people go there for a very reduced range of reasons.