I agree the many people assume that being on-site (visible) means they are controllable, engaged, focused, etc. but I think it’s far from true as a rule. What I mean is, it’s not a given. It depends on the person, the job, the environment, etc. – too many variables.
For me, most tasks are best done outside of an office. The only things that might be better are things like meetings and even that’s questionable (a meeting at a cafe might be better than a conf room).
Of course, coding and such is best done undisturbed.
However, many managers I’ve worked w/ in the past have a very different job type that tends towards walking in at any time to discuss something, change things, etc. It reminds me of the Maker/Manager Schedule.
Also, I suspect a lot of managers wd be very nervous to think their employees would do better by NOT being around them.