I think there is the germ issue for some ladies, which is legit. But they are in the wrong business if that's the case.
I think also some of the ladies don't kiss or DATY--or whatever act--because in their mind it means they are saving something "special" for their SO which only they share, thereby separating their professional sex life from their personal one, thereby allowing the SO to feel "special". It's delusional thinking, but I think we all delude ourselves from time to time.
I've also been with a lady or two who had DATY or kissing on the menu, but who I think sabotage that by eating onions or garlic prior to a date, or douching with something that is distasteful. It prevents what they want to prevent, without having to take it off the menu officially.