As indirectly pointed out in FMS New Schedule Type : Backup and run system-level script files, many of us compress our backups to save space on the backup drive. This has two main reasons - to be able to store more backups, and to be able to transfer the backup over network faster.
As also mentioned in the above idea, people typically use system-level scripting to accomplish that. Which has been good so far...
...until we got Encryption At Rest.
This great security feature unfortunately makes our databases nearly impossible to efficiently compress.
So in addition to not having to deal with system-level scripting, the option to compress backups before they are encrypted would let us make our backups smaller even if we also want them safe.
As you can see on the attached image, the impact can be significant: