Apple wants to get bumpers to iPhone 4 users as quickly as possible. That’s perhaps one reason why bumpers are now showing up at customer doorsteps without retail packaging.
As an added bonus, free bumpers delivered in this fashion won’t fetch much of a premium on eBay. Bumpers with retail packaging when sold on eBay may interfere with the legitimate bumper marketplace (yeah, first one is free but what happens if you want another color or style?!)
Oh, and it is much greener.