Magic Staff is (for mages from stories) tool to cast a spell. It is funny how in stories you are limited to a stick to cast spells.
Humans use Walking Sticks when they are old to help them move.
I am not limited by any of this but I still have a staff (I sometimes leave it behind to not attract attention).
My usage of the staff is for magic as booster and maintainer. I sometimes cast spells through it for bigger area of effect (and less of my focus / powers).