Various abilities force you to draw your weapon when there is no need for it. Abilities like rapid maneuvers and Dragon blood for a few examples make you draw your weapon to use them. It's annoying for rapid maneuvers because you run slower with your weapon drawn and end up having to resheath it every cast.
Probably other classes have their buff-type abilities that shouldn't force weapon draw when used as well. But please look at skills that you don't really need to pull out your weapon to use and make it so they dont do it.