Because -> is not a typical functional idiom, it's a macro specific to Clojure, and anything you can do with -> you can also do in the standard functional way, and beginners are better served by understanding the way a lisp works rather than only get taught syntactic sugars. Keep in mind that -> as a macro does not evaluate its arguments the way a function does, which complicates the understanding for a beginner tremendously, since Clojure is actually an eagerly-evaluated language.