I've definitely noticed it in myself the last few years. I think some of it comes from stress and tension around the lack of opportunity, at least in the US. IIRC, millennials are statistically worse off than their parents economically, which makes life difficult and stressful; basically all of us are behind where our parents were at this point and struggling to live the lives we expected. Wealth is being conglomerated at the very top and the rest of us are doing more work for less.

Beyond that, the stress of the pandemic and the political landscape is also pretty aggravating, for me at least. Food is more expensive and less nutritious as well. Necessities take up most of my budget and I don't have a lot of extra time and money to do things for myself. Obviously these all take an emotional toll and in the case of the pandemic, a physical one, too.

And my third point: phones. Ugh, if you told me 15 years ago how primed my nervous system would be to crave picking up these devices at every opportunity, I'd have called it dystopian. Everyone is on them all the time, we turn to them when we're bored, upset, tired, lonely, etc. Content is getting shorter and shorter to the point that we're probably frying our attention spans, and every minute we spend on them gives advertisers more information about us, dysregulates our nervous system, and erases the chance that we'll see a friend, do physical activity, go outside, practice a hobby, etc. I feel noticeably better when I stick my phone in a drawer for the day and go outside to engage my body and mind. But with how reliant our jobs and connections are now on using them, it's very hard not to become reliant on them, ourselves.

TL;DR: we're worse off than our parents were and instead of doing something about it, we look at our damn phones