I mean actively "pro-social", as in, encouraging and strengthening social bonds for the long term. In the same sense that "anti-social" really means things that degrade the bonds of social trust, rather than just someone quietly staying in one night.
For example - ringing elderly neighbours that you know are lonely or volunteering in the community or knocking on a new neighbour's door to welcome them to the area.
AIBU to think we don't really value those kinds of behaviours these days? It's easier for me to imagine a MN post complaining about creepy intrusive neighbours than someone being upset about not being welcomed. But then we have threads about how no-one feels safe to leave their doors unlocked anymore and we wonder how we got here...