People mostly don't have the problem because Ansible et al solve it for them. It's the classic situation of a good-enough solution existing, making the superior solution irrelevant.
Agree, what is going for Nix is that is a valuable tool and is very versatile. NixOS is just one application.
From OS point of view you no longer need:
- Kickstart
- Ansible, Saltstack et.al.
- Custom package repo for custom packages (if you need to customize something)
There are other areas too:
- create common developent environment, makes sure every developer has exactly the same tools installed with exactly same versions, so no more "it doesn't work on my machine"
- build system
- CI/CD
- packaging (as mentioned, you no longer need artifactory, instead you can have nix cache)
- there is also potential to use it for IaC, there's NixOps, but currently this is maybe the weakest part of Nix, it only covers deploying a box, but if you want to do something more complex, like autoscaled service it gets in the way. It is great for developing a new image though. There are terraform integrations, I didn't try them yet, might work better.
- you can configure local developer machine to use build system for local builds as well. If caching is configured, then once code is deployed it will already cache good build so it doesn't need to redo it
- for personal use with things like home-manager it can replace dot files as do more, you can have the same environment each time. Let say you change job and get a new laptop you can have it quickly set up the way you want it
