Actually a number of ads have content outside the bounding box for SD streams (though some SD streams now cut down things even more by letterboxing because of t

Actually a number of ads have content outside the bounding box for SD streams (though some SD streams now cut down things even more by letterboxing because of this). Ads were the first and still the most aggressive to have content strongly outside the 4:3 screen type. Because if you can create an effect that works it can be worth more than the whatever small number of users on SD, especially as those are likely out of demographic anyways.