If you are not cleaning your rabbit’s litter box every day, then it becomes a lot more difficult to know if he is using it or not. It is hard to tell if the piles of poop in the box are from today or yesterday or the day before, if it is not cleaned daily. Besides that, rabbits are very clean pets and tend to avoid a dirty box, not to mention that they eat more hay if you give it to them fresh in a clean box each day. Most people who have house rabbits put their rabbit’s hay into their litter box to encourage it’s use and to promote more grazing on the fresh hay.