Why do cats have 3 eyelids? Why don't cats blink?

I barely discovered this fact 2 years ago and yes it's true - Cats do have 3 eyelids while humans only have 2 eyelids. Many of you are probally wondering why they have 3 eyelids. The third eyelid covers almost the whole cornea of the eye and it acts as a barrier against any debris.
While the cat is in a relaxed state of mind, the third eyelid is hidden in the eye socket. Only a small portion is visible in the corner of the cat's eye. The skeletal muscles make the third eye move over the ocular surface from the inner, lower corner of the eye to the outer corner.

That is one of the reasons you don't see cats blinking that much. If you watch a cat closely, they will sometimes blink but it almost looks intentional. When a cat is pleased with it's surrounding, you see it blinking but rarely - this is because it is relaxed and doesn't have to put a guard up or be on alert as most cats are very aware of their surroundings.