It's a tradeoff. Not sharing files means that rogue/buggy apps can't mess up data from other apps, app developers can change file formats without worrying about

It's a tradeoff. Not sharing files means that rogue/buggy apps can't mess up data from other apps, app developers can change file formats without worrying about other apps reading their files, you don't need to worry about files left over after you delete an app, etc. On the flip side, nobody except Apple can implement utilities that work with "data regardless of what kind of data it is" - things like synchronization, compression, encryption. Personally, I agree with the OP in a sense that I don't like the choice that Apple made, but I can see their logic... And given that choice, what I would really like to see is more apps using UIFileSharingEnabled key, which allows me to copy files between app sandbox and my computer via iTunes - you hear me, Dropbox?