Why are you working so hard?

I'm guessing they're working harder to show their boss work will go on even better if he/she is not there. That will make the boss more inclined to miss out of work more often, giving his workers a more relaxed atmosphere to work in ie. less pressure. It's a type of psychological conditioning.

Oh! Thank you that makes much more sense now. Especially if hes a good boss then youd want him to be comfortable enough to be able to take care of himself mentally and physically if he knows his workers care enough to keep things going smoothly! Appreciated @terror !