A lot of people conflate “knowledge” and “intelligence.” Not the guy you replied to, they seem like a troll; but still, a lot of people.
Our ancestors had intelligence in spades. They figured out an insane amount of stuff just to survive; and it’s not too far back in the grand scheme of things that they had to remember it all because they had no way to record it. The first caveman to make a handaxe had absolutely no idea what he was doing, but they figured it out. Wheels, bows, fire, the entire concept of agriculture… They figured out how all of that worked from scratch, with no reference material.
Modern humanity builds on that with knowledge. We’ve figured out how to record everything our ancestors discovered, and all of our new discoveries as well. We’ve put men on the moon, figured out how to make electricity from things like waterfalls and glowing rocks, and almost everyone has a tiny computer in their pocket.
None of that means that we’re more intelligent now, though. All of that knowledge is iterative, so we’ve just been applying that same intelligence at a continually higher level throughout history.
Even for those who don’t build their identity around their job, a lot of folks are just used to having something to do.
I work in retail, and I’ve had a surprising number of old folks ask if we have any part time jobs available - they’re not looking for steady paycheck, they’re looking for something to do two or three days a week. Even if your job isn’t necessarily who you are, it’s still a reason to get out of the house.