Why do girls get turned on by kissing on neck?

Well, I've only had it happen once but it really turned me on. I think it's because it was gentle and normally it's add on to something else e.g pussy fingering or just a sexy touch. If you think about it that area is quite vulnerable (lot's of blood vessels), maybe it's a whole they make me feel safe thing. What kind of heavy breathing do you mean by the way?