Like many teens my only concern was about getting what (I) wanted. Personally speaking I'm someone who couldn't wait to reach adulthood. I hated being powerless, dependent, and requiring permission. Adulthood represented freedom and independence to me. Living away on a college campus was my first breath of fresh air and I loved it! Once I left school, got a job, and my own apartment I never looked back. I suppose my worldview is true freedom requires independence. You're not officially an adult unless you pay your own way in life.
Even then you have "adults" with children living under their parent's roof. You have to leave "the nest". Having a baby in my opinion doesn't make one an adult. There are also lots of teenage parents who are far from being adults.
Society will deem a person (irrespective of their age) as now an "authourity" because they have a "vulnerable helpless" person under their care. It isn't right. Has anyone ever written a parent manual?