I agree that I'm not representative of what the typical person should do in terms of fitness/training. But, I think that what people think is "healthy" now is pathetic. Just pathetic. One of my climbing partners is a lawyer and works in a high rise office building. One day we came back from having lunch and there was some sort of elevator control system malfunction, so none of the elevators were working. No problem, up the stairs we go. Well, holy hell, 99% of the people were gasping for air after one flight. You'd think they'd just scaled some Himalayan peak, and they'd gone a few steps. These weren't huge people - normal looking kinda folks, they're just pathetically weak. No muscular strength and no cardio-vascular capacity.
People live lives where they get out of a car, get into an elevator, or ride an escalator or moving sidewalk or whatever - self locomotion is increasingly rare. They don't have to carry things or lift things or move anything other than maybe a computer mouse.
Larry and I were 20-30 or more years older than a lot of the people on those stairs and our biggest challenge in the 24 flights we went up was getting around everyone bent over the railings trying to catch their breath.