Answer

Most likely because he’s a perfectly normal cat. It’s a natural instinct for cats to sleep most of the time. It’s an adaptation they developed in order to survive in the wild. Wild cats are hunters and predators. They are generally active only at times when there is food available. For short periods during the day they will hunt; the rest of the day, they conserve their energy by sleeping, eating, and just resting.

This is why your cat seems to have only two settings: "high speed" and "off." Lazing in the sun is just as much average kitty behavior as racing around the house and attacking everything in sight. If you’re worried that your cat sleeps more than most cats, you can take him to your veterinarian for a full exam.