In addition to backups, error correction data is a must for things you care about. With PAR2 you can add that to any type of file: https://en.wikipedia.org/wiki/Parchive
Bitrot is a thing, but mitigating it using par files seem suboptimal to me. The biggest problem is that you have to manually create the files (what if you forgot?) or write a script to do that for you (what if the script silently failed?). You're better off using RAID or a filesystem that has it built in (eg. ZFS or REFS).
It doesn't need to be manual. par2 is a command-line program, so it can be automated. Yes, ZFS is better for in-flight data, but it makes sense to create par2 files for your backup archive files, if you're then sending those files somewhere else (which of course you should).
