Why Do Cats Like Being Pet Above Their Tail?

Scent glands: The area above a cat's tail contains scent glands that release pheromones. When you pet this area, it helps spread these pheromones, marking your kitty as "familiar" and creating a sense of security and comfort.

It feels good: Cats have many nerve endings along their back and spine, including the area above their tail. Just like us, cats enjoy having those areas scratched - it feels plain good to them