I would phrase that differently: for many of their early 'users', Lisp was the object of study, not their tool. If your main question is not "I want this functionality, ASAP", but "how would I improve this tool?", it is normal to build a new, improved tool, rather than some app or library.

Ruby, perl, python, C, etc are tools for most people. People who do use them as study object will improve them by inventing a new language, rather than by tweaking them and still calling them by their original name. The main reason for that, I think, is that it is about as easy to implement a new language as it is to tweak those languages.