From my experience I would say it is plus or minus a 50/50 split. And I put no value into whether they state in their profile that they are into it or not. I have hired providers that state they are into it, then turn their head away if you make a move on them.
I have one regular that does not have it listed, and I made a move to kiss him during our second session, and before we were done my tonsils were nearly removed he was so good! And I am very happy he is a regular.
I have another regular that I always felt was a little shy. We would massage and play, but there always seemed like there was a boundary. Then one session, things got a little extra heated and before I knew it, he made the move on me.
Bottom line is it is hard to tell unless you try. I tend to not ask, but I will make a subtle move to try it and see where it goes based on the providers reaction. I also think there are other providers that will open the door to more things, kissing being one of them, once you have seen them a few times and are comfortable with one another.