It’s very useful when on a remote login where you don’t have root but want more modern software e.g. academic HPC clusters with shared filesystems, which tend to have extremely “conservative” OS versions (we are stuck on RHEL6 for the forseeable future).

I’m not aware of much else that fulfills this niche well - conda seems very very tied to precisely tested version combinations, and (from what I remember - tried and had problems) nix seems to want root/system level daemons.