Because people conflate exercise (gym, running, whatever) and activity. I can show you many people who degraded massively by not being active - i.e. not consist

Because people conflate exercise (gym, running, whatever) and activity. I can show you many people who degraded massively by not being active - i.e. not consistently walking and using their muscles (there's a reason why physical rehab involves actually moving). Where people are misled is thinking that you have to attend a gym or go running to be healthy - you don't. The grim reality is that you probably don't see many of the people that faded away and physically degraded by not being at all physically active, because they're very probably elderly and essentially housebound.