How can you be so certain that you know a truly representative sample of people in their 80s?
There are a very considerable number of people in that age range who are most certainly not really doing all that fine and whose physical and intellectual activity are nowhere near what they once were even ten years prior.
It's hard to know the mental and physical state of another person sometimes through a passing glance or cursory interaction. Sometimes even with more substantial interaction the true nature of their state can remain hidden from you. My grandmother, for instance, who is in her late 70s, experiences chronic pain in her knees. But I wouldn't have known that if my father hadn't told me; she generally does what she can to happily tolerate the severe pain when around family members.
There are a very considerable number of people in that age range who are most certainly not really doing all that fine and whose physical and intellectual activity are nowhere near what they once were even ten years prior.
It's hard to know the mental and physical state of another person sometimes through a passing glance or cursory interaction. Sometimes even with more substantial interaction the true nature of their state can remain hidden from you. My grandmother, for instance, who is in her late 70s, experiences chronic pain in her knees. But I wouldn't have known that if my father hadn't told me; she generally does what she can to happily tolerate the severe pain when around family members.