I don’t accept that all of those people intrinsically are lazy morons - maybe some or even most are, but a lot of people get that attitude metaphorically beaten into them by lazy and disengaged coworkers. I know this for a fact because I’ve witnessed it happen to many people as they mature as workers and also noticed it in myself. I can’t prove it’s not related to age, or position in life (eg a young single person eager to prove themselves at work, vs someone who prioritizes family) but I know firsthand that there are at least some experienced workers with families, responsibilities, and hobbies that manage to stay focused and engaged for a long time.
I expect some pushback against this, but I really do think this phenomenon - whatever you want to call it - is the basis for ageism. It frankly is a real, observable thing that life has a way of beating the passion out of people into a point they see their job as clock-in, clock-out. It doesn’t happen to everyone of course. One of the reasons I love working with interns and recent college grads is that, despite their lack of skills or knowledge in many areas, they mostly haven’t gone through that transformation yet.