[JeanPierre]

    If it is so good why ain't it is used more?

pg has written about this [1], and the main reason he found was that popularity is always self-perpetuating. If one of the languages get a head start with libraries, it's usually easier to develop programs and libraries within this language than other languages. If you know a popular language, you're more likely to have more job opportunities. If you're a manager, you would prefer to be able to replace programmers easily.

That's one of the reasons why Clojure started off on the JVM in the first place: It has libraries and an already thriving ecosystem. In addition, it's a nice bonus for language developers to not have to worry about performance related to GCing, threading, OS-specific differences etc, which the JVM abstracts away.

[1]: http://paulgraham.com/iflisp.html