I think you might be vastly understating the advantage here. I've been the guy who shipped software that "worked on my machine" but didn't work in production because on my machine there was a system installed dependency that got used but didn't exist in production and the only way to discover that was to ship to production. Nix makes that a far less likely scenario. It get's a lot of things wrong in how it achieves that but it fixes a real and very substantive problem.