In a very interesting article J. Harnik ties this to the woman’s entire body being a phallus:
in men the genital continues to be the centre of their narcissism, whilst in women there is a secondary narcissism which becomes attached to the body as a whole. (Hárnik, ‘The Various Developments Undergone by Narcissism in Men and in Women’, p. 69)
He even goes on to outline how the need to be admired, desired, or “loved” for one’s beauty exists in men as well in bisexuality, which is the case for all the positions:
This narcissism is strongly marked in a number of men whose love-life is also frequently characterized by a reversal of the typical relation between man and woman: they are attracted by a woman who falls in love with them and displays towards them the sexual overestimation appropriate to their own narcissistic valuation of themselves. It is entirely in accordance with our views on bisexuality to assume that a given psychic mechanism operates in both sexes, only more powerfully in the one than in the other… (ibid. 71)
Then he goes on to that beautiful, untroubled speculation that existed in the early days of analysis:
Thus the process commonly called 'genitalization' would play the largest part in the production of the charms of the female body. This view receives ready support from a consideration of the genital qualities developed by the female breasts, and especially the nipples. It is further confirmed by a statement of Ferenczi's with reference to the narcissistic significance of the face: 'I think it probable that the displacement of libidinal tendencies "from below upward" (Freud) which takes place in the sublimation period effects a secondary genitalization—probably with the help of the rich vascular innervation of the face—of the sexual rôle of the face, which is at first simply exhibitionistic. (By "genitalization" of any part of the body I understand, with Freud, a periodically intensified hyperæmia, oedema and turgescence, accompanied by corresponding nervous excitation.)'Indeed, one may go still further and postulate, as Radò once remarked to me personally, that this process may have prevailed in the evolution of the race as well and have led to the disappearance of hair from the face in women. This evolutional idea that the disappearance of hair from the face is due to the narcissistic desire to expose oneself is entirely in accordance with Sachs' statement, based on clinical observation, that the male exhibitionist displays his genital, whilst the form of exhibitionism which we regard as normal in women has reference to the other parts of the body, above all, to the face (ibid.p.73).