Kissing... why?

 I'm ace, and there's a lot about sexual attraction that eludes me. But the one that puzzles me the most is kissing. I can understand why someone would want to have sex with another person, and I can even kind of get kissing other parts of a person's body, like their neck. But kissing on the mouth? I just cannot understand it. It is so very unappealing to me and yet it is such a default romantic/sexual gesture. Such a default, in fact, that I have never really come across much of an explanation of why people like it. Descriptions I've read of kissing usually go for describing the texture of the other person's lips, how they taste (and I am always rather doubtful of the often flowery nature of those descriptions), and I guess the general intimacy of it? But is that really it? It's almost always presented as simply a given--you are attracted to a person, therefore you naturally want to kiss them.

So for anyone who does enjoy kissing and doesn't mind explaining exactly what you like about it, I would be very interested to hear your perspective.