Because not everyon has read The Sentry goddamnit. They're diffrent aspects of the same person. If you read any of the supplemental material by the writer he says that the biggest concept in it was a hero addicted to his powers, ala Hourman. This addiction is fed by him creating his own enemy, so that he will always be able to swoop in and save the day when other heros have failed, giving him both the huge adrenaline rush and the adoration of public and peers. The Void is an external manifistation of his desire to be the best hero imaginable, wich is a horrible thing when you've got undefined abilities and a flare for the dramatic.
