You probably don't agree with your cat's ideas for remodeling your living room. But your cat doesn't claw the couch or scrape the drapes because they're a bad kitty.
Cats scratch for many reasons: to remove the dead outer layer of their claws, to mark their territory by leaving both a visual mark and a scent (they have scent glands on their paws), and to stretch their bodies and flex their feet and claws.
Scratching is a normal, instinctive behavior and you don't want to discourage it completely. Instead, your goal should be getting your cat to scratch acceptable objects, like a scratching post.
