That's like saying you don't like the colors in the rainbow. Koa varies so much on both densities and color that you'd be hard pressed to prove that it's all the same species. The color of koa can range from light blonde to dark chocolate and everything in between and can include interesting contrasting grain patterns and "curl" as well. When it is worked properly and you have an understanding of the wood koa can yield an excellent sounding instrument. But that varies as well with the specific board used. I don't know of a wood that varies as much as koa and you simply can't treat one set of wood like another. I have bunches of koa here that I know would never make good sounding ukes. That stuff goes into the bin for future picture frames or other household projects. Sometimes it's sold as "students sets".
When you realize that the ukulele is indigenous to Hawaii (it evolved from Portugese instruments but became "ukulele" through it's influence and evolution in Hawaii) it stands to reason that the more treasured ukulele is one that will be built from koa, a tree that was pretty common here at one point. My own view is that it is chosen mostly out of tradition and (former) ease of availability here in the islands. If Hawaii was the birth place of lutes or violins we'd probably be making them out of koa as well! One thing I do know is that when people come to awaii looking to buy a uke they want a koa ukulele, not one made of zebra wood.
