To an extent and at some point, children (especially teens), will need to make their own decisions so that they may learn how to be responsible. Responsible decision making is a skill that must be mastered in order to mature and have self confidence.
Focusing on teens here, it is important to keep in mind that they can be very impulsive, often times not thinking things through. This is what can lead to getting themselves into trouble. The teenage brain is not yet fully developed and during adolescence the brain goes through quite a transformation. The part of the brain that is responsible for decision making is not fully developed until the mid-twenties. For this reason, I would say this may be the number one reason why teenagers need help when making important decisions.