At the end of the day, magica is most useful as a way to enhance tools. Raw magica, unless wielded with incredible skill and raw energy, will do less damage than a lightly enchanted sword or arrow.

It is akin to using raw physical strength vs wielding an object. Only the most skilled fighters use their hands more effectively than a person swinging a stout length of wood. 

There is however an excellent reason to use magica alone. Against demons and other highly magical beings, it seems to attack their energy *directly*. You can stab a demon many times, and still lose the fight. But magical attacks will wear them down shockingly fast, with enough direct hits. 

-On Magica, writings by Queen Augustine