> Most people need some trainings to be able to get into something new. If they have not been taught REPL driven programming, I don't think they can discover it by themselves, despite maybe hearing others talking about it constantly.

Does Emacs count? I don't know Clojure, but I learned elisp for programming emacs and I discovered myself the power of evaluating any part of the code I write on the fly, experimenting with it. It's really useful in practice.