Why does our rabbit eat the carpet when we bring him indoors?!?

Sensible answers only please. He is about three and a half months old ish and has been pulling and eating the carpet to start with at the edges but now its anywhere! He has plenty of food and water in his hutch and dosn't want for anything. Any advise would be appreciated as this is our first rabbit. Thank you. xx (ps we do stop him from doing this incase of choking)