Callum was a member of Squad One, raised from a lesser noble family and trained in the way of the sword and even taught in the ways of the nobles and dragons.
Unlike many commoners—which was a rank he was really close to—he was quite informed of the state of affairs within the Wall.
He knew of the futility of their lives in the eyes of the dragons. Humans were weak and barely worth anything. A human's value dropped considerably the more 'mundane and average' they became.
From having a weak mana core.... to being unable to fight... to having too much trouble interpreting the divine runes to become a rune specialist, one was only bound to become more and more useless to the dragons… and society at large.
Humans with powerful mana cores could study to become a Warlock while one with great knowledge of the runes could become a Rune Specialist. It was all a matter of who had more to offer.