I find it kind of funny that people need to turn to "science" to understand that exercise is good for us.
It makes total sense that the body will stay intact for a lot longer if it's actually being used and taken care of.
I like to explain it by having 2 motorcycles that are absolutely the same. One is being used and taken care of properly,
The other one is doing nothing, occasionally being sprayed with water and dirt, and perhaps even stored in a louzy environment.
Which motorcycle will survive after 10 years? The one that is being used, the other one will have rusted away.
The human body is even worse than a motorcycle, because it will slowly fall apart if we don't do anything about it.
Just like you said it with the motorbikes. The one used and taken care of will remain in good condition, so our body, when we take care of it, it does not "rust away"