Implementations and libraries are too balkanized. A problem which related languages like Common Lisp and Clojure don't have, and thus you're more likely to see

Implementations and libraries are too balkanized. A problem which related languages like Common Lisp and Clojure don't have, and thus you're more likely to see them in use. Even ultra-fans like Philip Greenspun (him of the eponymous tenth rule) picked more "batteries included" languages like Tcl when you had to interface with a database and web server. In recent years, things have improved (e.g. Racket or Chicken), but on the other hand, lots of other languages aiming at the same market share enjoy popularity (from the aforementioned Clojure to Ruby, Ocaml and JavaScript).