Yes, its used to guarantee reproducible scripts (so, e.g., you can use `jq` and not require someone have jq installed and not require running through docker) and dev environments as well (which is really great for both version locking as well as polyglot projects).
I use nix shell for development and reference uninstalled packages from scripts as well. I think we both understand what Nix is capable of. I still don't find any issue with my initial comment that Nix at its core is for maintaining a reproducible system from config files in git. My point wasn't to be pedantically perfect but rather to communicate a core use case in laymen's terms for the uninitiated.
I said "a lot more to it" as well...