Sophie, MumnGran makes a very sensible point: at the moment your parents are responsible for you.
That means they get to pay for your board and keep, they get to sort out any mess you find yourself in, they get to look after you if you are ill or unable to cope. Even illegal drinking is not just a problem for the young person concerned- if you lie to the person at the bar, the landlord risks losing his whole livelihood.
It follows logically that any trouble you get into can't just be your business: it is also the business of the people who will end up picking up the pieces. As long as you live in their house and rely on them, they will be affected by anything you do.
Before you complain about this too loudly it might be worth asking yourself the following questions:
would I be able to cope without them?
could I get and keep a job that is well paid enough to support me?
if I was ill or in trouble would I not expect them to sort me out?
can I genuinely say "no, I don't need you?