I don't think these sort of details matter much. The idea of the game is to get the players into the action as soon as possible. Our characters will know what they need to know in order to be bad ass action heroes. They're also empty shells (no backgrounds) because we're meant to inhabit them and instill ourselves into this character. Rather than being a puppeteer for an action hero that someone else fully fleshed out, we are the action heroes and this is our legend. It's just like the main character of Marathon, and to a lesser extent Master Chief, were empty shells for the same reason.