I'm sure many people don't even think about that. Having to reinstall all your packages from scratch is not something they do frequently.

And for the people who are looking to optimize the initial setup, there are many ways to do it without a declarative package manager. You can:

• Write a script for your initial setup that includes installing packages
• Use a tool like ansible
• Use meta-packages
• Export your currently installed packages to a file and pass that to the package manager on the new installation

Package metadata isn't stored in text files because there's an amazing technology called the database.

All you have to do is learn how to use your package manager. Spend time reading the man pages and learn the options, and you can query everything you need.

Maybe try guix

You can backup your list of packages to .txt and install from .txt using apt so I don't really know what more you would need. I literally just did it last week to install a new distro.

There are some package managers that do that.

Alpine Linux's apk stores a list of required packages for the current system in a single file, /etc/apk/world. using apk add or apk del adds or removes a package from this list, then calculates how to get to that stage (adding all the dependencies, resolving conflicts...) and then installs the needed stuff (and removes the unneeded) to make it match.

The file can be edited or replaced using any other tools, then apk fix will do the same recalculation and installation/removal steps.

But they do.

Example.

If i remember correctly you can pass a txt file to pacman when installing packages, but i could be wrong. There is also BlendOS, which from what i can tell has an immutable base, with a toml config on top of it to install the additional packages you want. Never tried it myself though. I also use NixOS because i wanted to be able to reproduce my riced out system more easily if i have to reinstall. I do wish this space had some more competition, because it might make this way of running a distro more approachable. The closest thing i've seen aside from guix is probably those ublue customized images that you can build, but i'm not sure how comparable that is.

You need some ansible love in your life!

Gentoo can do this with Portage sets. They’re essentially a more simple way of creating a meta package which just installs other packages. And you can also write config packages which installs configuration for other packages.

If I, a humble computer hobbyist can figure out Nix, why don’t more users do so, and why is Nix so niche?

My guess as to why this isn't a more central feature of Linux distros is that this is not something most users need. If you need to reinstall the OS because you broke it, then a full system backup is probably more convenient, even if it's less than optimal to back up packages which you could download. If you need to reinstall the OS because you want a clean slate when upgrading to a new version, then your package list for the old version could cause a lot of conflicts as maintainers regularly remove and add new packages.

I have backed up my zsh, vim, tmux, etc. configs and written a few shell scripts which install them and download vim plugins etc. If I ever need to reinstall the OS I would use these. However, in the last 20 years since I ditched Windows I have reinstalled Linux exactly two times: Once because I was an idiot and didn't have a proper backup when I accidentally formatted the wrong HDD, and once when I switched from Xubuntu to Fedora in which case a package list wouldn't have been usable.

Unless I'm missing something, you can do this fairly simply already. I have a post-install script I run on all of my machines which sets up all network shares and runs 'apt install whole bunch of packages' to get things into a ready-to-roll state.