It's not that big a deal doing it from scratch, but most users of Docker were already using it and have it setup to run as root. Undoing that is not trivial, definitely not as simple as just uninstalling and reinstalling rootless. You have to nuke your existing containers, images, and volumes, and depending on the package manager, it's not always obvious if uninstalling Docker will undo all the networking and user configuration changes it makes. Just out of curiosity, I uninstalled it on Arch right now and it didn't get rid of the docker0 virtual bridge device, it didn't remove the iptables rules, /var/lib/docker is still there with everything in it. The docker socket is still there, but I'm guessing that would go away if I rebooted, assuming the systemd unit creates that on login.