Nobody's saying the Aborigines didn't invent the didge.

As a rhythmic drone, it works very well for many kinds of music. Other instruments that do the same thing, despite working on totally different principles, are the utogardon, washtub bass, jug, gypsy "rolling" vocals and tambourin de Béarn. I don't see any problem with using a new instrument for a musical function that's already part of a tradition.