It's a fairly funny thing, this. Apparently some women believe that their partners are more turned on if they spread their vaginal fluids over their breasts. In terms of courtship, the smell of genitals is what links male and female mammals together during courtship, and that some animals use this scent to track their partner(s). There are some that think that this carries over to humans, and that each vagina's (and penis's, I guess) smell is unique. Obviously, though, I am the worst person to confirm this.*