I am 27 and I still have no clue.
Jesus you have an old head for one so young and naive. You have rights to be protected from that crap.
Okay , these restrictions are i place to protect kids . Children have rights , plenty of them .
You are asking why you're not legally allowed to do certain things , it's because you aren't mature enough to understand the total consequences of these acts . Whilst you feel restricted remember that certain good things come from this ( you aren't fully responsible in the eyes of the law , you can't acquire debt etc ) .
shouldn't you be in school
Rights are a fiction. Rights are bought with money and children are born in debt to protect the established feudal order.