This is a big reason for me. Also because if anything breaks - even if my system becomes unbootable - I can select the previous generation from the boot menu, and everything is back to working.
It’s very empowering, the combination of knowing that I won’t irrevocably break things, and that I won’t build up cruft from old packages and hand-edited config files. It’s given me confidence to tinker more than I did in other distros.
It sounds like you’re including NixOS in this category so I guess I have switched.
I also tried Fedora Silverblue a bit, and it seemed to me that ostree distros are built on a cool idea supported by compromises I didn’t like:
Some stuff doesn’t work in Flatpak sandboxing - at least not yet. One example that comes to mind is Firefox integration with the desktop 1Password app. Maybe I could make this work by tinkering with Flatseal, but when install the native packages in NixOS this interaction just works.
I don’t want my CLI tools in a container running a different distro. For example if I’m using Distrobox to set up a dev environment that’s installing a distro with traditional package management to get around not being able to install packages natively in the host OS. I get that Distrobox enables isolated dev environments for different projects. But for that use case I think Nix devshells are more flexible, robust, and performant.
Nix also has its problems - in particular the usual complaint that the documentation is not comprehensive enough to match the complexity of the system.