We don't let the other person know out of all types of fears. Fear of rejection(that they'll say I know you do and I'm not intereseted at all), Fear of looking stupid(See previous fear), Fear of a change of relationship(Now thats is known even though both parties know anyhow). I remember this time when I was 5 years old and I was playing doctor with this girl that lived down the street. We were play buddy and we saw each other about 3-4 times a week. Well kids do get curious and excited and somehow or another she agree to take of her underwear and layed down in the floor on her stomach and I rub'd her bare butt for about 2 minutes. Then went into the bathroom and I said I'll show you my lower front if you show me yours, and she got a kind of aggitated look on her face and was like "HELL NO", and I said WHY NOT its a FAIR TRADE - your front for my front, She said NO then she left, I've been emotionaly scarred every since, and have a sort of disstain for how women try to over vaulize the vagina and under appreciate the penis.