There are three common reasons for this common cat behavior.
First, cats need to scratch. Cat scratching will help eliminate the outer layer of the claw. Scratching also exercises the muscles of the cat’s shoulders and legs. Think humans stretching when waking up in the morning.
Second, other than just putting territorial marks, cats also leave their scent. Cat paws have scent glands between the toes that secrete pheromones. Through scratching, pheromones are transferred. This will inform other cats that a cat already “owns” the area.
Third, scratching is a stress reliever for your cat. Your cat may like to scratch when excited, frustrated, happy or anxious.
It is important for every cat owner to understand cat scratching. Make sure that you provide your cat a scratching post.
Learn more about Cat Behavior at Makati Dog and Cat Hospital
Sources:
http://www.cat-world.com.au/Cat-Care-Articles/cat-questions.html
https://www.petfinder.com/cats/cat-problems/why-cat-scratches-furniture/
http://www.catbehaviorassociates.com/furniture-scratching/