The 'drawing area' behind artboards limits where you can place items, especially masked items that fall off this area, limits number of artboards, and limits how freely I can place multiple artboards.
If you want 40 artboards (for say storyboarding) but want more than 10pixels between each, you can't. If you have masked a large drawing and need the invisible masked items to sit outside the Dark Grey drawing area, you can't. If you have a lot of artboards but want to place characters for use by other designers, animators outside your artboards but have many artboards you struggle.