Rabbits have to gnaw all the time to keep their teeth in check. Their teeth grow continually. If they get too long, they'll starve and die. Even wild rabbits do this and your's will be no different, you just won't be aware of it.
There's a fascinating book called "the private life of Mr Rabbit" that goes into extensive detail on rabbits and their physiology. Did you know that rabbits are one of the very few species that when pregnant, if the conditions become unfavourable to the survival of the litter, can re-absorb the foetuses and not give birth. It saves energy and resources when fire or other disasters or just unfavourable conditions occur.