Many women do not masturbate.
They do not touch their vaginas.
Sex is not the same as masturbation; being receptive and having someone fuck you is completely different from exploring your body. Particularly one, as NJ pointed out, is hidden, which is not the only factor. There were classes that taught women masturbation, many of those out there for men?
I am very sexual and it took years masturbating before I was able to learn how to make myself cum, and forget about consistently, that took even longer. With men it is there and hard... obvious. With women it is more exploring and getting to know your body, then you have to relax and let yourself cum once you find your spots. Some women never find their spots and never orgasm, or orgasm only after a lot of work, and give up because nothing happened. I'm not saying they are frigid, just not masturbators.
Wow woman body is really more complicated that most men thought !!!
According to most studies or statistics most woman masturbate , not as often as men but most do . Why the woman of the samples would lie saying that they do masturbate?