> I find it weird that I've been living in the same building for 7 years and I know basically nothing about my neighbors

Isn't this just par for the course when living in dense settings?

I've been living in my current apartment for more than three years, and I'm pretty sure I wouldn't recognize most of my neighbors if I randomly saw them in the street. We say hello when our paths cross coming and going, but that's it.

Many people come to the cities specifically looking to be more anonymous. You can't have that if everybody knows everybody.