It’s always teenagers and kids that are meant to save or explore the universe. Did you ever imagine why that could be? I mean, there are some obvious answers right? Younger characters can bring in a wider audience than series with older adult protagonists who carry adult problems with them. Younger characters in series are easily much more family focused and thus can bring in more attention from a large pool of viewers. Possibly the reason why there are so many more high school shows. So besides the meta, what reason could there be.
My own idea on why some series chose to focus on younger protagonists comes with my theories of Gundam. Why was Amuro Ray, at 16 years old, the one to get into the seat of a gundam compared to a well trained adult. Well, obviously it’s a coming of age story right? My theory comes from what most Americans do around 16 years old, learn how to drive a car. Now, the car theory doesn’t work when it comes to Japan or some other countries but it’s the same principle. Cars are a key way for characters to experience their first sense of freedom. So putting that sort of story into Gundam, where the cars are giant war machines.
Some things in Gundam can also be attributed to generational trauma too. In a scenario where two sides are at war or one system has a strong hold over its people, a lot of adults living in that current era are not going to try to change that world for the better. It takes some teens old enough to at least drive a car to save the world. It also takes kids fresh from the system to try and change it. Even if they don’t succeed, they are the ones who are going to try to change the world for the better for the future. The world themselves may be against them, but that doesn’t matter. If they can’t change things, it’s up to the next generation.
I also think that loss of innocence is an easy tap into for a series to develop drama. Adults who already lost it long ago are a draw for some people, including me, but losing innocence is an experience that so many people tap into.I did say easy, because a lot of series do it in their own ways. Some series can take that introduction into the real world in some of the cruelest ways and can be so well written that it can be an incredible piece of fiction that will be forever long lasting. The wrong hands can just make it into some of the cheapest trite possible that no one can check out. Handled well, and our young kids can work great. Handled worse, and nothing will come from it.
Mechanical Anime Reviews 
Hmm, you have some good points about the benefits of younger main characters. I think that having teenagers as main characters is also an easy way to add drama to a series just because teens tend to be more dramatic, rash, and willing to jump to action, while most adults would/should be more cautious, level headed, and methodical.
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That’s also very true and the teenagers themselves make the drama a lot more realistic.
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