

It’s not. SELinux predates Fedora. Fedora went all-in on SELinux pretty early on though (a few other older distros too, but Fedora is one of the few remaining with significant mind-share), and many other distros decided not to do security at all for many years.
AppArmor is “sufficient” if you only want to deal with known-in-advance high risk applications being locked down, which was the approach most other distros took since it’s extremely complex to have a policy for absolutely everything (like SELinix requires).
In the latest distros using AppArmor, it’s been expanding so much that it is arguably easier to just implement SELinux and derive from Fedora’s Standard Policy. Ubuntu 24.04 for example was been broken by thier various AppArmor bugs for almost 1.5 years after release, all because they slapped system-wide AppArmor policy restrictions on the default system and didn’t coordinate any of it.
SELinux also doesn’t mutate the store unless the package in the store failed to set an SELinix file label. Providing the labels in most cases is trivial, so trivial in most cases that a global SELinux Nix policy package exists in a number of distros that can set normal defaults that work for most things.





And it’s only necessary because Nix doesn’t include it. Which is the only way anything is allowed to run on an SELinux system. SELinux doesn’t require Nix mutation, it requires Nix to be complete.
There are workarounds to fix Nix’s incomplete definitions, but most end users opt for the easy post-install solution that ends up mutating thier store rather than including the fix as a unique derivation for every package to add the missing SElinux labels and policy.