I did a little research on this over the past year. I interviewed five or six women in some detail about this. What I found is that most had KatawaGrey’s response. They like giving pleasure, and they like the feeling of control. It gives them a sense of power. In addition, and this really surprised me, they told me they liked the taste and feel of ejaculate.
I think that, on average, women have slightly better empathy than men. When they are doing this, I think they really identify just a tiny bit more strongly with their lover than men do, when performing the analogous action on the woman. I think they identify so strongly with their lover, that it is almost as if they can feel what their lover feels.
It’s also a very concrete thing. You can tell when a man is done very easily. It’s like the reward for the work.
Anyway, I was very skeptical about all this, but the story was pretty much universal. These were also women who said they really liked sex, and weren’t getting enough.
If I talked to women who didn’t like sex, I suspect the story would be different.