Why hasn't Peyton Manning been on the cover of Madden yet?

He's been the best player in the league for years now and he hasn't even been on the cover of Madden. Dante Culpepper, Michael Vick, Brett Favre, Donovan McNabb, and Vince Young have all been on the cover and they couldn't even hold his water bottle. I would love to see my favorite player on the cover even though its supposed to be a "Madden Curse". Why do you think he hasn't been on there yet?