He can do this precisely because he's finally got confidence in his ability to be independent. This new and surprisingly pleasant creature isn't dependent on the family anymore for rigid rules on how to behave, think, and make decisions, but neither does he have to reject parental opinions outright. A more comfortable balance is struck. The older teen can seek and listen to family advice, weigh it, and then decide on a course of action that may or may not be consistent with the family's recommendations. Young adolescents are just learning what it's like to rely more on themselves and this new taste of autonomy is often confusing.
Kids are keenly aware of all the inconsistencies that accompany their moves toward independence.
In some instances autonomous behavior is rewarded by parents, while in others, it gets them grounded. Although the distinction between different behaviors and their resulting consequences makes sense to parents, to young teenagers it seems arbitrary. Parents are apt to experience a variety of emotions as they deal with their adolescent's fitful lurches toward independence. Some feel rejected and bristle at being taken for granted. It's hard not to take things personally and realize that much of a teen's irritating behavior can be chalked up to things that are done in the service of growing up.