Etymologically, they sure do. For all of its warts, elisp has not only many users but many programmers who have created some pretty complicated stuff. It's definitely a contender.

Popular has many meanings. If one takes popular to mean done/used by many then sure. You are right. Filing tax returns is popular by the same definition.

If you mean popular as in the antonym of unpopular I don't think elisp can be called popular. I have written several thousand lines of elisp outside of my Emacs config, and it is probably my least favourite lisp - and I believe most people who know more lisps than elisp think like I do.