I think part of it is that you have a higher reimplementation rate for your code in languages like Clojure. If something takes you 3 hours in Java and you find its a crap design, you might take 15-30 minutes to figure that out in Clojure.
It has the side-effect of teaching you to think through your ideas more (wait, I thought we were supposed to avoid side effects! ;) )
It has the side-effect of teaching you to think through your ideas more (wait, I thought we were supposed to avoid side effects! ;) )