This is my neighbor to the T. He is older, almost 73 but he is always complaining of being out of breath, or gets dizzy when doing manual labor and is always saying "I need to talk to my Dr. about this, I shouldn't be getting out of breath"I'm in healthcare and can say that a large majority of people I see choose not to get and/or stay healthy. They use the medical system to keep them "healthy" thinking that there is a pill to fix everything.
However, the guy never walks or works past the point of being uncomfortable so he is out of shape in all ways. My dad on the other hand walks and works every day and is much more healthy and active because of it.
Mobility is the biggest factor as we age IMO, once we lose our ability or want to MOVE our health goes to shit pretty quickly.
There are a lot of other factors but if someone could do what they need to stay mobile I think it would go a long way.