The quarterback is the most important position in all of football and, in all likelihood, in all of major professional sports. No other player is responsible for more of the cerebral part of the game, no other player takes as much blame for losses, and no other player gets as much credit for wins as the quarterback.
This is not to say that QB Winz is a valid stat. After all, the quarterback is not the only reason why a team is victorious or not — an atrocious offensive line can get him out of his comfort zone while a terrible defense can lead to losses when a quarterback plays well enough that, in a vacuum, you would think that his team would get a win.