> Are there many (or even any) people in that situation, though?

Probably not (except those who made that project).

> Who decides they want a script-able editor, but then chooses one scripted in a language they don't like and don't want to learn?

Mostly because the scripting language is not the first thing you think about when using an editor (just guessing here; I don’t have data on that). I started using Vim because its editing capabilities are quite powerful but its scripting language is really bad. Emacs’ LISP is great, but I can’t get used to the way Emacs commands work.

Why not? Elisp is not amazing but having a DSL and powerful metaprogramming lets you script things so much easier than a lot of languages. Viml is atrocious. There are some libraries tha use the metaprogramming to make it easier to program in as well. Vim is a good idea and makes editing text nice to use. Emacs is a good idea that everything is customizable and has a good level of abstraction to make things happen. Using evil inside Emacs makes a great editor. Spacemacs makes Emacs easier to use too with the mnemonic and ergonomic bindings and a mostly good ootb experience for how young it is.