IMO, it all depends on your outlook towards animals. If they have enough space to be active enough to stay healthy both physically and mentally I wouldn't think a run would be necessary. However, as others have said, they seem to enjoy being outside immensely and if I am capable of providing them with access to the outdoors, I would not in good conscience be able to restrict them from it completely. There are show horses that live in stalls and dogs that live in apartments, but both are usually allowed access to room for physical activity which keeps them healthy.