What can Djokovic possibly have better to do than this?
The whole point of being a pro tennis player is to deny other pro tennis players of success.
Djokovic should be doing all in his power to deny Federer statistics that he can fall back on to argue that he is the greatest of all time.
You're really misguided if you think the whole point of being a tennis player is to deny others of success, and not strive for what will maximize your own success. Playing a challenger or 250 would probably throw off Novak's entire preparation for the Olympics and in the long run could cause him to lose the #1 rank again even if he got it back.