On some level, strangers are easier to connect with than people who are in your life more permanently, like neighbors. Maybe there are fewer expectations and more mutual curiosity. It seems backwards, but for dipping your toe into more personal connection, it is an easier path.
This is funny but true. I don't think I've spoken to my neighbors in any place I've lived in 10 years other than maybe awkwardly running into each other in the hallway.
In apartments this has always been the case for me. I moved in to a townhouse recently and the neighbours on one side spend half the day gardening out the front so I do end up talking to them.
I think it would be nice if apartment buildings prioritised making some communal space that’s comfortable to hang out in so you’d have a chance to chat with people who live in the building. Usually it’s just some token couch in the lobby.