There may be a number of reasons why a cat might like to play with its owner's hair. First of all, cats do have the habit of licking each other's fur. This is a social behavior used to establish and maintain social relationships. If your cat likes you and accepts you as its companion, it may imitate this behavior and help you "groom" it.

Secondly, the cat may be interested in your hair because it smells the fragrance of the shampoo. Some cats may like the smell of a particular shampoo and even think of it as a "cat grass" smell.