The entire provider experience IS my fantasy. Why would I want to think about someone else? I want to enjoy every second of the encounter.
On a related topic, for years I have been asking my play partners what their fantasy is while masturbating. It is very helpful to get to know your partner and what turns her on in order for the love making to be more enjoyable. Communication is the key to good sex. Not ONE WOMAN has ever given me an answer so far. They either give a very vague answer, or change the subject quickly. This includes women who otherwise have been very open with their thoughts.
So it is my conclusion that either their masturbation fantasy is on the other side of the line when it comes to sharing, or that it is so wierd and freaky that they would be embarrased to share it.