The usage report is cumulative, not instantaneous. The act of checking probably isn't a significant fraction of their phone usage. So if for a given usage pat

The usage report is cumulative, not instantaneous. The act of checking probably isn't a significant fraction of their phone usage. So if for a given usage pattern the screen does consume 60+% (which is what I often see) then keeping it off all the time certainly helps ... but also makes the phone a lot less useful!