From my experience this doesn't happen to younger people only. I've made a similar observation with people in mine and my family's circles which range all the way from ages 20s to 60s.
So how did even the behavior of people that were used to a different conduct change? The question one must ask is, "why do people meet up in the first place and why would they be worried about canceling meetings"?
It's about fulfilling needs, namely entertainment and social interaction. Before the internet became mainstream there wasn't an easy appealing way for a lot people to pass the time without going out to begin with so there was little reason to be lazy and sit on a couch all day. Talking could be done on the phone if you had the money but you couldn't share anything non-verbal that way. Today you have a plethora of options to distract you on the internet and you can share everything on social media and safely quench your feelings of isolation. Social media is also the safety net that shelters you from the consequences of keeping people hanging. So what if people don't wanna hang out with you anymore? You always have a place to retreat to to get your fix.
All of this comes with the fact that real interactions are just a lot less convenient. Planning, committing to a time frame, the effort of actually getting somewhere with just the outlook of a possible payoff. It's very tempting when you consider your options and realize you can get gratified instantly with no effort. It may even seem like a completely rational choice. There's a reason platforms like Tiktok are becoming increasingly popular. They're not designed to give you the highest joy possible, but simply stay as frustration free and convenient as possible. Even if you didn't like something, at least it was short, painless and took no effort.
Convenience runs deep in our society. For longer than our history humanity has tried to make life easier. Like the now common wisdom, "if you want a hard job done easier, let a lazy person do it", technology itself has been there mainly as a tool for convenience, not to make us stronger but to make the world an easier place. It goes so far that we define our very progress by the advancement of our convenience. Progress is not a measure of how tall we stand but how high we can stack the laurels we sit on and while technology used to be focused on making production more convenient with the advent of computers technology finally brings ultimate convenience to entertainment and social interaction.
One thing I noticed with videogames, which are specifically designed to be fun, is that most memorable moments weren't actually that fun. A lot of memories were made during frustration and struggle, but are the most valuable in hindsight. It made me realize convenience is basically like candy. It satisfies in the short term, but it's addictive and unhealthy. And in the same way getting in shape is only truly satisfiying when you can think back on all the hard work you did and see your body not just as a reflection of your results but as the effort and discipline you put into it.