Weapon arts were different from simple martial arts. They were a sub-branch like spells, albeit with caveats more distinct than the mere heavier expression of a core's nature.
Those techniques' main difference was their need for magical weapons, adding an expensive variable most cultivators couldn't afford.
The availability of magical weapons was another variable. Such tools weren't easy to find, especially in a suitable shape and rank.
Lastly, a cultivator's mastery had to be taken into account. Not everyone could perform a weapon art as long as all the right tools were in place, not well, at least.
Much had to align to make performing those arts at a satisfying level possible, seemingly rendering the investment pointless. At least, it would be unworthy of the effort if it weren't for the simplest compensating factor of them all.
