I've wondered about that not just in relation to fantasies but in relation to sexuality in general.
I think, fundamentally, most women do not feel physically, emotionally or socially safe enough with unknown or slightly known men to risk it.
Physical safety - we know that if we ask a man to stop doing something sexual and he does not want to, we are very unlikely to be able to make him.
Emotional safety - we know that men do not have to respect or value a woman to be happy to fuck her. Other than those women for whom it is a specific fantasy, knowing your partner may look at you like dirt in the morning is not sexy.
Social safety - women who are known to be sexual, especially in kink/non standard ways, face both intrusive curiosity and value judgement. Knowing that her social status could be affected by knowledge about her sex life also makes women risk averse.
This is not to ignore that some women have found outlets like swinging, sex parties etc where they do feel safe. Though I note that these are all groups with some degree of social rule enforcement.