Although some of you gave me a little too much information, there's no doubt that most people become sexually active too early. We know this from hindsight, don't we?
From what I can remember, the pressure to become sexually active as a teenager is probably the biggest thing on your average 15-year old's mind (if they haven't already). It's the yard-stick by which teenagers measure each other; woe to the kid who graduates high school a virgin... Or not. In fact, after going to a community college and transferring to a good 4 year university, I learned that a lot of the successful students never had sex in high school. They were probably shunned by the cool kids and weren't invited to the best parties, but none of that mattered because the cool kids were flipping burgers while they were earning degrees.
In our society we have no ritual for becoming an adult, but adolescents desire to be perceived as adults and, to some extent, to undertake adult responsibilities. Lacking any other certification of adulthood, it's no surprise that sex is the substitute.
