[bloaf]

"...the tough thing about adulthood is that it starts before you even know it starts, when you're already a dozen decisions into it. But what you need to know, Todd, no Lifeguard is watching anymore. You're on your own. You're your own man, and the decisions you make now are yours and yours alone from here until the end. "

An arbitrary age of maturity has nothing to do with actual (as opposed to legal) adulthood or responsibility. The fact is that "kids" at the age of 17 and 18 are already making decisions that will affect them for the rest of their lives. Making the legal age later will certainly not help these people realize that the decisions they are making are important or that they need to take responsibility for themselves.