This thread has gone on for ages, so I might as well add to it!!
The way I see it there are 2 basic types of clients. The first wants to get his rocks off, and often to try a bunch of sExual stuff that he doesn't get a chance to, for whatever reason. He doesn't really care if the girl seems to be into it, as long as she performs.
The second is looking for an experience that mimics real life attraction. In addition to the obvious release, he values the mutual enjoyment of both parties, and wants to be made to feel like a desirable sexual human being. The avoidance of th kiss is an in your face reminder that he is "paying for it".
Of course an overgeneralization, but I suspect it applies to many. I fall into the latter category, and no kissing is more or less a deal breaker for me- it's really the one restriction I can't live with.
Of course I repect the right for any provider not to provide services she doesn't feel comfortable doing with strangers. I'll choose my encounters accordingly.