According to david elkind, teenagers question society's rules and become involved in idealistic causes because they can:

They are thinking too concretely to understand the world. David Elkind think this is because the teenager goes to the stage of formal operation of thinking at age 12 and they learn to be more critical about the things that surround them, this kind of thinking leads them to be very concrete in their way of seeing the world and consider more their defects and those of the people around them, this is why they tend to be rebels.

I hope my answer can help you.