User blog comment:Maslab/On the subject of Noble Six/@comment-356904-20130712080122/@comment-1210220-20130712185053

Probably because Six is you, the player. He/She is your own customised SPARTAN-III with a backstory as a 'Hyper-Lethal' badass. While Six gets very few lines in-game, I'd have to guess that the player was supposed to project their own personality onto the character and make their own backstory, to some extent. Its that air of mystery that has inspired a number of fanon characters that interpret Six's past differently, and do so well without making them survive Reach.