Studies show that as many as 60% of women have rape fantasies and I am one of them. Many theories have been suggested to explain why this is the case.
My theory is that women are genetically inclined to want the male they are having sex with to cum. We want to be absolutely certain that he cums and that actually excites us sexually. The most certain way to be sure that he has or will come is if he is dominant and makes it clear that the sexual experience is for his pleasure. So we get mentally excited when we imagine that we are not enjoying the sex and he is because we are sure that it means he will cum. The point of the sex has nothing to do with our pleasure, his pleasure is the focus and therefore the likelihood that he comes is higher.
The other theories about wanting to be ultimately desired or free of the guilt associated with sex also makes sense, but I just wanted to add this theory to the pot.
See this article: How feminism ruined my sex life.