Sadly child soldiers are a thing though. In real life they happen in poor countries like Afghanistan, the Central African Republic, the Democratic Republic of Congo, Iraq, Myanmar, Nigeria, Somalia, South Sudan, Syria, Yemen etc. So it's possible that these Stormtroopers are being taken from poorer worlds, possibly on the Outer Rim. Even during the time of the Republic things like slavery still existed on far off worlds like Tatooine. As Shmi Skywalker explained to Padmé, in these worlds civilisation just doesn't exist. And we see this still happening in the period of the Original Trilogy (Tatooine is still a lawless world controlled by gangsters) and we know that it happens in the Sequels too. Just look at Jakku. We now know that Rey was an indentured child slave herself.

But think about it, there are multiple countries in our world today which recruits child soldiers, including terrorist organisations like Islamic State and the Christian Lord's Resistance Army etc. The LRA's use of child soldiers was briefly brought to the world's attention with the #Kony2012 movement... but then everyone promptly forgot about it, cos hey, it's 2013 and Oppan Gangnam Style! The Syrian conflict has displaced more people than WWII () but we don't care because it's not happening in a developed Western country. We cared for a little while in 2015 when photos of a drowned 3 year old boy's body washed ashore in Turkey. Since then we sometimes care... we see video or photos of victims... bombings, chemical attacks... horrible stuff. But then we forget about it.

Think about it... what do we call a basic foot soldier in an army? Infantry. From the Latin word 'infans' meaning small child. Obviously most infantry are made up of adults, but the word itself still draws its origins from when children were used as arrow fodder. Lots and lots and lots of children going missing and joining armies around the world today, yet we turn a blind eye to it on a daily basis.