They are used to push through the lockscreen e.g. when you get a call or when a timer finishes. I assume camera apps might also use it for the button shortcut (double-tapping the power button opens your camera in most Android phones). If the app doesn't do calls or alarms of some type, I can't really think of any valid reason why they would need that permission unless it's something weird like Tasker and you want it to.
Other permissions that are also "revoked by default" like this are using the accessibility services or drawing over the screen - you just need to have a popup in your app that says "the app needs <permission> to work, please enable it in the following screen" and then opens the settings page.