Maybe the problem here is the definition of “utilization”. Arguably 100% utilization should be what you get when someone is performing at peak efficiency, not w

Maybe the problem here is the definition of “utilization”. Arguably 100% utilization should be what you get when someone is performing at peak efficiency, not when they're doing work every minute they are at work. And peak efficiency is shown in many places to require NOT doing work every minute you're “working”, both for physical and non-physical work. Even ignoring serendipitous thinking and the other mentioned advantages of not being at 100%, you have a simple benefit you get from not being at 100%: rest. Sometimes it isn't thinking time. Sometimes you don't spend it exploring. Sometimes you don't innovate. Sometimes your brain (or body) just needs a rest. To think about the TV show you like. Or about what you're doing tonight. Or what your kids are up to at school. Occasional rest during the day is as important, in my mind, as getting good sleep at night. And acknowledging that that's a part of being productive is important, because otherwise you start feeling guilty when you take those short rest moments (or you don't take them at all), and that eliminates half the benefit.