Middle-aged, in the US. From my perspective, a lot of the change is due to overbooked children. My wife and I have a group of ~5 couples that we used to get together with regularly. Before any kids, it was ad-hoc, often out somewhere (dinner, bar, whatever). When the first couple had an infant, that changed to pot-lucks at their house (easy to put the kid down for the night). But now that 3 of the couples have kids, 2 of which are in middle-school, it's almost impossible to get the gang together - one of the kids always has some practice or another event. We still get tougher in smaller groups, but less frequently.

This is counter to when I was a kid - it was rare that I had a scheduled sports event on a Friday or Saturday evening. During the day, sure. But 6pm+ on Friday? Basically never. But that seems to be common now. Travel sports, so lots of weekends totally away, or specialized coaching at odd hours, or just a 3rd activity to pad that college application. It's crazy. I honestly have no idea how kids have any fun today (and I say that as somebody who played 2 varsity sports, one instrument, and was an Eagle Scout - but through middle school, I still had plenty of time for just hanging out - it was common to ride my bike for hours on a Sunday - into town, get an ice cream, across the river into DC, and back).