JerryM, the point is that ANY increase in fitness can help, in all sorts of ways. And without meaning to attack any individual, I have to say the following:
I have been to over two dozen countries as either a Navy officer or a defense contractor. It is generally easy to pick out Americans. They are fat, and they don't walk anywhere, but they are tall and have good teeth. Generally speaking, they are often oblivious to or in denial over their lack of fitness.
You say some people just can't exercise. I call those people "quadriplegics."
I had a female friend in college who worked out, despite debilitating MS. On days when she could not walk, she would train on machines and let them guide the motion, but she had no give-up in her.
Problem she then had was she looked healthy, so people thought she was pulling a scam when she parked in handicapped spaces, or that she was drunk when she swayed while walking.
But she made the most of what she had.