In the world of cats, licking is not only a way of cleaning their own hair, but also a social behavior. When a cat licks another cat, it usually means they are building a relationship, increasing trust and friendship. Therefore, when a cat licks your face, it can be understood that it is trying to establish a closer relationship with you and express affection and trust in you.

Also, a cat licking your face may be a way to express dominance. In the cat world, cats with high status will lick cats with low status to show their authority. While domestic cats don't typically have any real fear or respect for us humans, they still retain some of this instinctive behavior.