system
Given the following post, respond as if you're commenting on Reddit:
human
[Mech Anime] Why are Teenagers such a vital part of our planetary defense systems?

Are adolescents better predisposed to pilot giant robots or use magical powers to defend our planet then trained adult soliders, or is it the end result of a recruiting/PR push to get children interested in the Xenomilitary?
gpt
While each universe is different, most of them have specific reasons why teens are used.  Sometimes they are uniquely qualified due to brain patterns (Evangellion).  Often we come into the war after decades of combat leading to younger and younger soldiers (Mobile Suit Gundam series).  In other instances we are looking at people trained from a very young age and pushed into service (Gundam Wing).  Finally, there are still other series where the protagonists have just joined the military and were never supposed to be in these types of combat.

Its also important to note that there are series where most pilots (or all pilots) are adults instead of teens.  G Gundam is almost entirely adult pilots, and the only teens in Gundam Wing are the specially trained hastily sent protagonists, everyone else is an adult.