If you go back to thousands of years in the cave era, men were supposed to go hunting. It would take one day, two day, five days, seven days, but they would come back with a bounty. They would give it to the woman. Woman would divide it amongst the children and make sure that the neighboring woman's child doesn't come and eat that. Men needed to procreate. They had little time at home. Men are wired to have sex quickly ejaculate and go. So as a protective thing, women are wired in such a manner that they need to be stimulated at more than one center, maybe multiple centers before they are ready for sex. Biologically, does this mean more nerve endings in other body? That's right. So they're all together. Only then she would want somebody to have sex.