Answer
Flo:
Because cats like warm , Comfortable places that provide security . This may also be a out of adoration
Anonymous:
Cats like to share body warmth with those they trusts and other cats,
and cats don't see humans different from their own so they are being
nice.
Gary:
YOU can never own a cat.
The cat OWNS YOU.
Setting on you (or on your clothes or books or anything else you have) is the cat's way of saying, "You are my human that is mine and I luv them."
Anonymous:
Cats are schemers, she's going to slowly move up to the throat and then "sleep" on your face so you die.
Tim:
Cats are warmth junkies and you are warm.
