Comment by MarcScott

This is probably because I'm on NixOS but I have never used nix-env to install anything.

I use nix-shell to test out a package, or use one that I only need temporarily.

If I need a package for a particular build then it gets added to my config files, and I rebuild switch.

If I don't want that package anymore, then I remove it from my config and do another rebuild.

I've never really understood the use case for nix-env.