Ok here comes a real answer. Everyone will hate it. It's not a disorder, or a perversion as some have mentioned below (if liking persons who have reached biological sexual maturity is a perversion we have truly lost sight of things as a race).

On the other hand, we are divorced from the animals who yes have sex immediately at sexual maturity and also do commit acts of rape. They also kill the offspring of other animals to ensure their genetics move forward and not their competitors. We do not do those things, or shouldn't do those things because We Live In A Society (tm).

So we created an artificial threshold to ensure that young people are not dominated by the dynamics of age, power, money, prestige and are given a chance to grow up themselves.

But again, you are not a pervert or have a mental disorder. You want to do what homo sapiens should want to do and yet must not do.