Things tend to become real messy when playing through many classes and becomes unorganized. For example ill give a better idea... My paladin got many defensive cool downs and they are all located in one action bar (lets say its the 3rd action bar) and im using useful keybinds for them...and now i switch to a healer and i have less defensive cooldowns obviously so now i HAVE to put an attacking/healing spell on my defensive cooldown action bar just to use that specific keybind which is stuck in the 3rd action bar. So now i have healing spells spread everywhere and becomes messy.