Kissing goes back to our Neanderthal early human brain. Kissing, 50,000 years ago was a way of passing food. From mother to baby, or to help a sick old guy. When a woman 'kisses' a man (or child), she is nourishing and caring for him or her. The same applies to male, to a lesser extent.
When males kiss a woman it is a dramatic display of 'approval'. A familiar bonding ritual not necessarily involving sex. Essentially saying, I love you. You are part of my tribe.