And the reason that LISP code tends to be reluctant to split things out into mul...

And the reason that LISP code tends to be reluctant to split things out into multiple forms with variable assignment IMO is because it introduces a new level of nesting. It's too much friction to go from

    (defn foo [] 
       (+ 1 2))

    (defn foo []
      (let [x 2]
         (+ 1 x)))

I wish that there were some kind of macro available in Clojure that would provide a local "def" kind of functionality that doesn't pollute the namespace and just creates a binding in the parent scope. So that you could do something like:

    (defn foo []
       (let! x 2) 
       (+ 1 x))