They presumably don't publish apps that use exploits to help the user gain root without unlocking the bootloader and wiping the data partition.
Androids built in app backup functions are woefully incomplete, and switching to a new phone recently I had to relogin to most apps and re-set up nearly everything, except for stuff like contacts and anything from google. At least some apps supported exporting settings to external files and allowed re-importing them.
When I do run into apps that are difficult to run, I make sure to give them 1-star reviews. I consider attempts to block rooted devices from running an app to be malware.
I don't think I knew it was on the Play store. It's a free download from the website, but paid on the Play store. I'd like to make a donation without giving Google a cut - the author deserves to get paid.