I haven't worked with it too much, but being on the JVM is one of the things I like about Clojure. The JVM has a huge standard library, but I don't really like Java so Clojure gives me a way to use all that existing code in a language I enjoy writing. There are definitely some downsides to the canonical implementation being on the JVM, but any move away from that is going to end up "wasting" a lot of effort reimplementing all of that library and I just don't see it being worth it, at least at this point.