The absence in iOS of documents and data in settings

What is the reason why Apple Inc since the inception of IOS has not made available a simple mtethod for deleting whatever is contained in the area under settings 'documents and data'. I am currently using an iPad Air 32GB running iOS 9.0.2 -, not jail-broken at.

Example: user wishes to delete a file in Keynote. User deletes file. File vanishes iwithin application.

But...

Go to 'Settings'- General- Storage and iCloud- Manage Storage. Select application ,in this case Keynote, and what I find is a continually growing 'Documents and Data' dialogue box with documents and data I cannot access let alone delete.

When the user deletes a file in iOS, I am given to believe that due to encryption the file becomes randomised garbage irrecoverable to all except computer forensics. ( How can we really know?)

...and why has Apple Inc removed third party utilities like iShredder from ProtectStar from doing a rather good job of trash collection in IOS? If anyone has purchased this utility, have they experienced its sudden removal from the AppStore and the 'Purchased' list?

In summary, I have two concerns : security and usability.