@hawkeye10,
It's not arbitrary, Hawkeye, and it's not "a construct stemming from affluence", the human brain continues to develop until about the mid-20's. We know that now because we have better ways of charting and measuring and evaluating neurological brain development than we previously had. We used to think adult brain development had been reached by age 18.
Trayvon Martin was not an adult, not legally, and not developmentally. Emotionally, and neurologically, a barely 17 year old is not an adult, he's still a child. It is quite correct to refer to him as a child. And it's because he was a child, that he couldn't buy cigarettes or beer, in that 7/11 store.
And there is a definite reason auto insurance premiums are much higher in that age group. In addition to allowing them to have driver's licenses, would you also want to see barely 17 year olds have the right to obtain permits to carry concealed weapons as well? Should Trayvon Martin have been as legally armed as George Zimmerman that night?