It doesn't conform to the Filesystem Hierarchy Standard, and that leads to issues with other external tools. Recently I had an issue with pip installing a library in a virtual environment that links to compiled platform libraries. It broke because the libraries weren't in the usual paths.
#nixos is truly amazing. I've never had to "reinstall" nixos. I've had the same fresh install since 2016. in fact, everytime you switch to a new system state, its effectively a "fresh install".
kernel panic? no problem, nixos installs previous system states as boot menu entries. just rollback. something I've done many times.
using any other linux distro is literally just a waste of your time, unless you like reinstalling your system all the time when it gets in a bad state.
"just use macos" you might say. well macos updates and breaks shit all the time. my desktop never changes, because I have no desktop. just xmonad and custom app launcher I wrote (https://github.com/jb55/cmdtree ).
nixos is the bitcoin of linux distros. no surprises, a bedrock of reliability.