Puberty is only the onset of hormonal changes that signal sexual maturity. However, one's brain does not fully mature until the person is at least in his or her twenties or beyond.
They have to start somewhere. Also, the armed forces have deemed that they can recruit 18 year olds, and the cigarette lobbies want to sell smokes, so they push "up" adulthood by pushing "down" the so-called age of adulthood so they can increase their profits. The alcohol producers also want this to happen, but so far, their lobbyists have been unsuccessful calling 18 year olds "adults".
in some cultures it does...
the jewish culture
...you crazy Diamond....
Because you might look like an adult, but that doesn't mean you act like one.
The former generation still thinks of their kids as kids even though biologically they're not.
you will understand the answer when you get to adulthood
Why rush becoming an adult. Adulthood is all about taking on life and being responsible for your actions. Puberty is all about hormones and no responsibility for your actions.
Because you don't have an adult life.
like new shoes takes a while to "grow into them"
Because you can't stop the aging process.
But immaturity can last a lifetime!
Because it's during puberty that people starts learning what it's like to be an adult.