My, completely unqualified, theory is that it is evolutionary. The hardcore 3rd wave feminists talk about how men have evolved to rape women. The men that raped the most women, passed their genes on the most. Compound this over hundreds of thousands of years from the Horn of Africa to today. What the really haven't thought about, is how, if this hypothesis is true, then the reflection of that is also true. Women have evolved to be raped by men.
By that I mean, the women who fought back 'too much' were beaten and often died. Over hundreds of thousands of years, the genes that generated that behaviour disapeared. But, the women who became arosed by being raped didn't fight back, they survived, often becoming pregnant, and over hundreds of thousands of years, those genes flourished.
Of course, I could just be chatting out of my ass.