You are confusing work with labour. Having a job isn't natural, but doing stuff is. And if you actually stop doing stuff - i. e. just lie in bed, doing nothing - your body quickly start to suffer and then pretty much decompose.

I would go as far as to say you need labour to be healthy. You need some kind of physical labour (be that sport, gym or something else) to be fit, and for your body to function properly. And you need to use your head to not be bored and go insane - to read, to think, to solve problems etc