I believe it is depending on people background, culture and values. There are countries that even men kiss each other in the lips, like Russia. There are countries that give two kisses, one in each cheek as a normal greeting, like Spain. In Cuba we most of the time give one kiss in one of the cheek once we feel confident enough which happens to be most of the time a couple of minutes after meeting someone. lol Some other cultures I believe consider wrong or inappropriate to kiss anyone expect the close family members and they even limit the physical contact with other people.
In Cuba people usually don’t kiss their kids on their lips but I remember we see with amazement how Russians that lived in Cuba kiss each other in their lips even their kids. I have a slight memory from my mom kissing me on the lips but I must had been very little.
I do kiss my kids in the lips and I don’t see any wrong about it. My younger son when he was very little didn’t let me kiss him and he didn’t kiss too much anybody either. His way to show affection was only by hugging and I accepted his way. Then when about 2 years old he started kissing me on my lips and then his brother who is 10 months older than him at about the same time the little one started to kiss me he stop doing it. Now both of them kiss me all the time. Sometimes I am busy doing something and they just came for a kiss and to tell me that they love me or they like me, give me a hug and keep going on whatever they were doing before. Even my 7 years old daughter kiss me on my lips and it doesn’t bother me at all. I am glad they feel that close to me and wanted to show me their affection and love for me that way.