There are many reasons, but consider this. Too often we adults want our teens to be something that many of us adults never became. Teens tend to be very idealistic. Ethics, determining what is good and evil, is important to teens. It is quite true that their system for determining what is good or evil is commonly very different from our system.
Teenagers hate hypocrisy.
When it comes to knowing what is going on, teens are very savvy. The teen information network rivals any adult network ever developed. There is no formula. There is no guaranteed process. There are many factors involved.