Do we treat children fairly?

From Wikepedia:

"Age determined by each state; the minimum age is 6 (North Carolina),[2][3] however, only 15 states have set minimum ages,[2] which range from 6 to 12 years. States without statutory minimum ages rely on common law, which means that 7[4] is the minimum age in most states; for federal crimes the age has been set at 10."

From another website:

"In the United States, dozens of 13- and 14-year-old children have been sentenced to life imprisonment with no possibility of parole after being prosecuted as adults. While the United States Supreme Court recently declared that death by execution is unconstitutional for juveniles, young children continue to be sentenced to die in prison with very little scrutiny or review. EJI has documented 73 cases where children 14 years of age or younger have been condemned to death in prison. Almost all of these kids currently lack legal representation and in most of these cases the propriety and constitutionality of their extreme sentences has never been reviewed."

http://www.eji.org/eji/childrenprison/deathinprison

If a child can be held responsible for a crime at age 7 and be tried as an adult for murder at age 14, why can't they legally drink? Why can't they drive? Why can't they vote? Why can't they choose to not attend school?