The problem is that apps need certain permissions to perform their function. Such as a music app that needs access to the phone module, so it can pause the music when a phone call arrives. This has the effect of users not paying attention the the specific permissions, since in many cases the need for them isn't obvious.
Why? Why doesn’t the operating system do that for them? Why is it up to individual applications to decide whether or not they want to pause music with a phone call starts?
Here's another one: app needs the storage permission to attach a diagnostic log file to a bug report email. An OS that sandboxes applications should absolutely provide a way to do this without additional permissions (a file that was only ever written by the app cannot contain data not available to the app to begin with); as it is, either the user starts ignoring permission prompts because otherwise things don't work, or they deny them and the developer can't get a log file.
