Personally I don't mind kissing but I can understand why several girls would not. Kissing IS more intimate than sex, especially to women. Its science. Kissing is connotative of love, commitment, passion, vulnerability, and respect.
Sex, can mean several of these things as well, but its actually connected to a part of our brain thats more instinctive - more about basic mechanical reproduction.
Kissing became something analogous of romance fairly recently in human evolution, while sex, obviously, has always been around - and for a large majority of human history had nothing to do with anything but survival of the human race. Sex was as much as a part of life as hunting and gathering. Kissing came around thousands of years later as the human emotional spectrum and overall social structures evolved.
Also, young girls are raised around fairytales, barbie dolls, harliquin (sp?) novels, etc that perpetuate the idea of kissing = love (not sex equals love), and the moment of the kiss is the climax of solid commitment. Actually, several modern plotlines in movies and books geared towards 18-25yr old females involve meaningless sex or seemingly meaningless sex leaving the woman in a state of limbo until a passionate kiss in the rain (or something equally dramatic) proves his desire to now be in a monogamous relationship with her and her alone.
Unfortunately, the difference between a kiss and sex to a woman is not the same to many men. Studies have proven that a large percentage of men when engaged in or watching a kiss register is as just another sexual activity.
Long story short, when a female experiences a kiss biology takes over and emotions are automatically involved that are not necessarily involved in sex alone. These may or may not be emotions she wants to share with a client. Clients may be left befuddled because they simply do not have the same biological and pshycological makeup as females, because their role in sex has not gone through the same changes that the female role has experienced throughout human evolution.
/end dork rant