I see this in other social situations too (though social may be stretching it a little bit) e.g. in the gym, on the bike paths, and inside my apartment complex. I'm in my early 50s and people in their 20s and 30s aren't interested in saying hello in a polite way (and as neighbours especially), whereas older people (my age or older) are always interested in at least being friendly.

You can argue that, in gyms and on the bike path, people are more focused on their goal, but I still find in those situations that oldies are happy to chat for a bit, but younger people just want to block you out.

TBH I hate saying "young people" in this way. I feel like I'm running them down for what is their choice, and that feels bad. But it is something I have noticed in general i.e. not just 1 or 2 individuals.

I recently went back to studying, and it's almost the opposite there. Lots of people need "tutorial/lab friends," and so the barriers to conversation are really low. You literally stand next to someone and bam, instant friend (at least during the lab).