The old saying a kiss is just a kiss really isn't all that accurate. Some kisses are much better than others and some people view kissing much differently. Human males and females view kissing very differently in most cases.
In the dating world, if you asked most people what they look at first in a prospective date, they will more times than not say lips. Especially men. A lot of men are attracted by red lips, which is why it is used in so many forms of advertising. Red lips some say equate to the look of ripe fruit or the color of some animals body parts when they are ready to mate. For a lot of men, lips are equated with another body orifice to be used during sex. For a lot of men, kissing is a means to an end. It's not something they enjoy necessarily, but in their minds and make ups, it is the doorway for more. Some men would rather skip it all together and get on with the sex. Kissing just doesn't do the same thing for most men that it does for women.
Women on the other hand, equate kissing with all kinds of things in regards to the relationship. They equate the kiss with the man's feelings for them. They tend to judge kisses by how they are performed. Some women have a tendency to end relationships over kisses alone because they tie them to so much more than just two lips meeting. For women, kissing is an integral part of a relationship not a means to an end. For some women, kissing can determine whether the relationship moves forward to sex or not.
Kissing produces chemical reactions in the body including dopamine and serotonin. Both of these chemicals produce intense feelings akin to a drug induced high and also feelings much the same as those of obsessive-compulsives. Kissing produces much the same chemical reaction in the body as does falling in love. For some women, the act of kissing can so mimic that of falling in love that they want that almost as if craving a drug. Men for the most part are all about the moving on.
A kiss is just a kiss doesn't seem so likely anymore, now does it?