i think it all goes back to our culture in general. men have always made full use of prostitution with little or no social consequences whereas women could do no such thing. If a woman was a prostitute she was a social outclass, whereas respectable women could not have sex at all untill they were married. I think we carry remnants of that in our society. If a woman has sex she is looked down on, so once that has happened why not sleep with every guy possible, after all, she is already a "slut" but women who wish to avoid that stigma have to keep their leg tight
since gys never had that stigma to deal with they can be much more honest about their passions