I think the pandemic has had a lot to do with it. I'm autistic and have never liked sitting very close to people, even as a child. I dislike unexpected touch. Social distancing was great (although lots of other things about that time were not) but that has meant for many people it was harder to go back to being packed in like sardines in places.
I'm actually on a train right now and people SMELL. Like BO, sweaty, wet dog kind of smell. It's vile.
If we're going to talk about previous generations, let's think about all the overstimulating things they DIDN'T have to put up with. All the things my late Nanny used to moan about "not in my day"! The population is bigger, for a start. There's just more of us. Everywhere.
People eat CONSTANTLY. Everyone on this goddamn train seems to be eating something. Packets rattling, competing smells everywhere. Snacking was not part of the culture until probably the 1970s. My Polish grandparents especially considered it unforgivably rude to eat on public transport and people don't do it there now unless they're tourists. Nowadays, people are constantly stuffing their faces, because they can. Which also means that people are bigger, and the size of seats hasn't kept up with the size of people. It's not in companies' interests to make seats larger, so you get "spilled on" if someone much bigger does sit next to you. Severe obesity was extremely rare back then.
People wouldn't have drunk alcohol on public transport or got very drunk in restaurants, cinemas, etc - again, would have been considered rude/unacceptable and they'd have got chucked out. But you get groups of loud, lairy, drunk people (men in particular) in all kinds of places now, they're no longer confined to the pub or social club.
Previous generations didn't have smartphones. People play their music, videos, phone calls on loudspeaker all the time, which I think is rude and intrusive. I don't go to the cinema any more because people don't turn their damn phones off, screens are lighting up the whole time, and they're sat there chomping the whole way through the film. Just on this train journey there are at least three people in one carriage doing it. The competing, clashing noises - ugh. Even NC headphones don't totally block it.
A young man on the Tube the other day was so absorbed in scrolling he didn't notice an older lady with a walking stick had got on. He had to be told by another passenger that she needed the priority seat he was sat in, and he looked absolutely outraged at the interruption to his scrolling. More so than having to give up his seat. He didn't acknowledge the older lady at all, got up with his head still buried in his phone.
Shops and restaurants now play loud music, punctuated by lots of different announcements, which they didn't do in my grandparents' day.
Everyone is chronically overstimulated, and at the same time chronically bored, hence why we can't cope without a screen, a snack, etc.
My grandparents' generation had to deal with a tiny fraction of the inputsvand cognitive load we now do in modern society. It's simply not comparable and I would argue many of the behaviours people display now are not "normal" and many people have lost all sense of consideration for those around them. And because of some of those behaviours, and the level of environmental stimulation we are all subject to, we have probably become less tolerant of the normal ones.