Not American.

One big thing I feel contributing to this is a lack of time.

And the more strange unusual thing, many folks basically have "school nights", they don't do anything because they're going to work the next day.

Perhaps work becoming more mentally intensive makes this more difficult.

You might be on to something. I am one of those school nights people. Having people over will kill all "me-time" for that evening - once you get them out of the house, you do the dishes and it's straight to bed, usually. Meaning I had zero time for myself, I was hosting. The idea of having no "me-time" between two work days is hell for me. It was OK in my 20s and 30s, but not now in middle age.