It's not a matter of necessity, it's a matter of "why are we fixing what isn't broken", if you feel having one button will suddenly make you a more efficient and better player, then by all means you can play like that in PvP as much as you want. But, why should anyone be forced to re-learn their job rotation and redo their muscle memory because some people absolutely need one button or they consider the entire job dysfunctional is beyond me.
This wasn't even an issue until they made changes to PvP and people saw what they did. It's funny how that happened.