First, they have a need to work the coating off their claws from time to time. They do this by shredding your furniture and whatever else they can get to. You can get your cat a scratching post, and likely she'll use it from time to time, but will she use it exclusively? Ours had an awesome scratching post, and she used it very energetically, as long as she happened to be in that room when she felt like scratching the crap out of something. When in other rooms she scratched whatever she damn well felt like scratching, and over the years has ruined a sofa, a loveseat, draperies, carpets, and who knows what else.