Has anyone here used scripting languages on a microcontroller? And if so why? For user-scripting? I can't really think of another practical use case but there are multiple implementations of pretty high-level languages out there so someone must be using them.

You'd have to build some hardware abstraction to use with the scripting language anyways at which point you could just use the language you wrote the abstraction in imo. Is it so you can have inexperienced (cheaper?) devs do the maintainence? For all the embedded projects I worked on the high level program logic wasn't the thing that took the most effort.