I live in the Netherlands, where cycling is common, even for old people. It's not a scientific observation, but I can definitely see the difference in health between old people who bought a car as soon as they could afford it (for the working classes, car ownership didn't become normal until the 1960s) and people who continued to live like they always did.
My grandmother is almost 85 and she's still on her bike almost every day. Walking longer distances (more than a few km) has become difficult for her because her hip starts to hurt, but she's still able to cycle about 5km to visit church, the grocery store or friends. She's afraid of heavy traffic, so sometimes she walks with her bike instead of riding it. She's using it like some kind of walking frame. She has a friend in his early 90s who still cycles 5 km to church every morning at 7am.
I know quite a few very active elderly people, but the sad fact is you don't see the inactive ones that much because they've either passed away or their health doesn't allow them to go out much.