They're very much like firefighters. Firefighters spend the vast majority of their working hours either literally doing nothing or else doing somewhat pointless make work, like washing the fire truck.

If your firefighters are spending more than ~10% of their time doing their actual job, then the odds of them needing to be in two places at once reaches unacceptable levels.

Old fashioned secretaries are similar, if less extreme. An executive secretary's main job is not to do secretarial work, but to be available at a moment's notice. If they're busy, they're not generally available.