It is up to the developer to support iCloud backups.
Even so, other than disaster recover and moving to a new iOS device, iCloud backups are not a good solution. You can only restore your entire device, and you only get the last backup made (not a history of files). This, along with the rather limited 5GB of free iCloud space is probably why your app does not support iCloud backups.
For real security/recover of your files in iOS, be sure to save them elsewhere.
That's not so say iCloud backups are bad. For what they do, they're great. But I'm pretty sure I'm not alone in wishing iCloud would become a better solution for individual file history and recover. Then again, I've got the extra iCloud space to support those kind of features. Most don't.