Keys 1 through = are not enough, and keys 5 or 6 > to the right are too far of a reach. It's much faster and easier to "feel" or do a keypress without looking or accidentally hitting something I don't want to when instead I just hold my pinky down (since it hovers over shift) and press the same movement keys or 1-5 to give me a different ability.
WoW happens fast, it's nothing like ffxi. Most aspects take lots of spamming of several abilities, if you have to look, feel around, click, or anything like that; you are being that much less efficient. Some moments randomly in a fight where I need to use this ability which is more uncommon over something I've been spamming, it's nice to be able to do it in the same exact reaction time by pretty much pressing the same exact key.
XI Wiki


