Its especially beneficial when you're doing multithreading work. I've debugged multithreading C++ and multithreaded elixir/erlang and fixing errors and identifying race conditions is night and day.
We wrote a front end in highly disciplined functional JavaScript on react with a single source of truth object in the center. I haven't touched JavaScript in a decade, and I could debug parts and add features with 100% confidence that I wasn't messing anything up (needed the frontend in a pinch so we hadn't done unit testing yet-i know I know, it's fixed now)
If you are curious, I recommend the video "boundaries" by Gary Bernhardt, of "wat" fame.