Once you build a docker image, you can distribute that artifact reliably. But building docker images is highly error prone, at the mercy of non-determinism, var

Once you build a docker image, you can distribute that artifact reliably. But building docker images is highly error prone, at the mercy of non-determinism, various failure modes of package managers, and mutable state from web servers you don't control. In practice, you can't depend on it working without active maintenance and disciplined usage. With Nix, if it built once, it will build again, consistently and deterministically. It reduces fear of changing things because it just works. You don't have to cross your fingers and hope the build succeeds this time.