Security theater for marketing purposes. End users have no way of verifying that their cloud backups are encrypted, and Apple is the same company that complied with the NSA's illegal, unconstitutional conspiracy to conduct warrantless bulk surveillance on American citizens and lie about it to congress: PRISM.

Fortunately, no intelligence officials faced any consequences whatsoever for perjuring themselves to congress, or for engaging in a unconstitutional criminal conspiracy, so we can trust that the system of laws we've developed is working as intended and that this will never happen again.