The permissions system does not exist only for the user. In fact, as described here (https://developer.apple.com/library/mac/documentation/Security/Conceptual/A

The permissions system does not exist only for the user. In fact, as described here (https://developer.apple.com/library/mac/documentation/Security/Conceptual/AppSandboxDesignGuide/AboutAppSandbox/AboutAppSandbox.html https://developer.apple.com/library/mac/documentation/Securi...), the primary purpose of sandboxing apps is to help developers secure their apps. "By limiting access to resources on a per-app basis, App Sandbox provides a last line of defense against the theft, corruption, or deletion of user data if an attacker successfully exploits security holes in your app or the frameworks it is linked against." As such, from the developer's perspective the ideal permissions system should actually be as fine grained as possible to let the developers minimize the exposure of their apps. Android's permissions system was probably designed from this point of view.