I set it up this way so that if I need to reinstall Linux, I can just overwrite / while preserving /home and just keep working after a new install with very few hiccups.
Even with a single partition for / and /home you can keep the contents of /home during a reinstall by simple not formatting the partitions again. I know when I tried years ago with Ubuntu years ago the installed asked if I wanted to remove the system folders for you. But even if the installer does not you can delete them manually before hand. Installers wont touch /home contents if you don’t format the drive (or any files outside the system folders they care about).
Though I would still backup everything inside /home before any attempt at a reinstall as mistakes do happen no matter what process you decide to go with.