>>149392774
It's a cultural thing. Japanese society has always had higher expectations for the young to mature, to the point where elementary schoolers are still encouraged to walk on the city on their own to buy groceries and teens take public transport to highschool. Kids in the west have been helicoptered for over 20 years now and are naturally not seen as being as reliable or capable of problem-solving as relatable twentysomethings with jobs, so for a lot stories with stakes having kid MCs would be seen as goofy, unrealistic or "socially unresponsible".