you can even bring your own bottled drinks/liquid on Japan domestic flights. they have a machine specifically for "scanning" drink/liquid. put your bottle on it, green light, then off you go. not sure how it works
25 years ago i used to live in public housing in HK where there are around ~60 apartments (~400 sq. ft) each floor. hallway interactions are common, we even leave the door open so people can have a quick chat when neighbor passes by.
Nowadays more people live in private housing, usually 8-10 apartments each floor. And people hardly know the last name of their neighbors. Not knowing who lives next door is the norm in HK private/subsidized housing now...