And, well, there's also no way a race of aliens that just happened to touch down, speaks no trade, nor yamataigo, nor the language Neshaten speaks(the name slips my mind), to just so happen to be able to forge Durandium and know the composition and how to treat it.
I also would agree with Skully, increased variety for different races, with metals that do somewhat the same, though functions differently, is in my opinion, a good thing. It makes sense for races to have their own metals and such and it thematically fits.