All the impractical exotic weapons in D&D are almost universally of elvish design. The elves, of course, have decades to centuries to master these weapons, letting them develop unpredictable techniques that all but the most dedicated of other races just don't have the time for when a sword or axe will usually do just as well.

Those of extra planar design are usually just born into the minds of their wielders, creating an instinctual ability to use them, formed by a travelling psychic intelligence obsessed with battle.