@ The sex is taboo bit, it's just like that saying, "life is what you make of it". Mass media, the government, and religions has brainwashed us into thinking it's taboo. Another reason is that a lot of people like to give a bit tmi, the same reason the word poop is taboo.
Also I think Psycho Bugler has a good point there. Teen sex is something appleasing, yet, it is a waste of hormones that we need.