Why is this aimed at ~30yo in particular?

Growing up, my parents and grandparents had the same neighbours for decades, even in apartment buildings. Of course they knew and talked to each other frequently. Hanging out in each others' apartments also happened on occasion, drinking some pálinka and listening to the radio. My dad used to go down to the ground floor to watch the evening news and story time at the superintendent's apartment along with the other children in the building. The only person who had TV in their commie block.

This already changed a bit in the late 80s / early 90s when I was growing up. People started moving around or dying. Out of the city to live in burbs. Or just left for another country. My dad was also less jovial with people as he couldn't stand stupid, so he often drove neighbours he disliked away.

Once I grew up, I moved into the apartment of my late grandparents. I still talked to my direct neighbour on a weekly basis, but by this time most everyone else died or moved away. Also I had to introduce my girlfriend now wife to my neighbour at least monthly due to her... seemingly selective dementia.

I'm in my forties now, and both at this and my previous apartment I've made sure to always say hi to neighbours. Oddly at the current place, the thirty something year old neighbours approached me first, stating they do some sort of communal hippy living here. They seemed friendly but then also moved away within a year or so.