Out of curiosity, which cultures have this strong sense of informal community? It sounds kind of great.
Before the smart phone I think it was less odd to pop in if you were in the area, but with phones, I feel like anywhere I lived people would at the very least send a message.
I think the mobile phone (original, not just smart phone) killed it to some extent as you would arrange things on the phone and not pop in.
With the ability and expectation that you can contact anyone at any time and make or change plans, doing anything unannounced has become unexpected. It used to be much more normal.
This sometimes still happened within the past decade in rural Virginia (my family owned a farm there). Neighbor farmers would stop by once a week or so and just chat, usually still sitting in their truck. Seemed like they were on their way somewhere and saw us outside so they'd pull over to talk.