Life Without Parole, Crimes Committed When 14 or Younger

Not much to add to the title. In the August Harper's Index this little tidbit popped up - there are 73 Americans serving life without parole for crimes they committed when they were 14 or younger (the source is the Equal Justice Initiative out of Montgomery, Alabama). Undoubtedly some of these crimes were horrendous and tragic and brutal, maybe all of them. But we are talking about children. A minimum of four years away from the age they are deemed responsible enough to vote; a minimum of two years away from the age they are deemed responsible enough to drive; a minimum of seven years away from the age they are deemed responsible enough to drink alcohol. Am I supposed to believe that the "greatest" country in the world can't figure this out some other way?