Agreed that rx is nice, but really only useful if you're writing elisp. 90%+ of people who need to interact with Emacs regexps aren't writing an elisp program - they're using Emacs interactively, or even using another program (busybox, GNU find, etc.) that uses Emacs regexps for historical reasons. For those people the differences in syntax between Emacs regexps and "normal" regex dialects are a pain.