It's one of the most annoying things about iOS. When I'm in an app that only works in landscape and I want to close an app and go into another one quickly, I don't want to have to rotate the phone just to open an app and then have to rotate it again once I'm in the new app. The iPad supports a landscape homescreen, why doesn't the iPhone? They could at least offer it and allow those that don't want it to disable it.