JVM Languages

What's the deal with so many JVM based languages nowadays like Clojure, Scala, Ceylon, Groovy? Besides obvious multiplatform support is there a reason for them to be JVM based or even make JVM ports of current languages? I still don't get the point of stuff like Jython.
Let's see if we can get at least a few posts without mention of FORCED COLLECTION OF GARBAGE

>>1
JVM is like Multiculturalism. It has brain washed the masses into believing in its cause, despite being rotten to the core. Once enough people realize it is nothing more than a tool used by Oracle and Google to subvert developers to their Marxist service-oriented e-Solutions, it will be cast away into the frozen void.