Clojure was specifically designed to have multiple target implementations. That's the why it's approachable. As for why it's desirable, clojure is a high-level

Clojure was specifically designed to have multiple target implementations. That's the why it's approachable. As for why it's desirable, clojure is a high-level language and as such has certain niceties that are difficult to give up when forced to drop down to a lower level.