Cats like scratching because it stretches their muscles and it removes the old claws. Plus scratching is a way to mark their territory, which is at least cleaner than urinating everywhere.
Yet if you want to keep your cats from scratching valuable furniture, you may need to get scratching posts and put them in strategic areas. Furthermore, you need to make your current furniture unattractive to scratching by spraying it with citrus scented sprays (cats don’t like citrus) or taping aluminum foil to your furniture.
The goal is to discourage your cat from scratching your furniture and encourage it to attack the scratching posts instead. Then again, cats will pretty much do what they want so you have to get used to them ignoring anything you want them to do anyway.