A request comes in: a form fill, a voicemail, a text to somebody's cell. Whoever owns the calendar reads it, works out what is actually being booked and how long it needs, checks availability, and replies with a couple of options. Then they wait. By the time the answer comes back, one of those slots is gone, so the whole loop starts over. That is a normal booking on a good day.
Reschedules are worse, because they cascade. Move one job and the travel between sites stops making sense. Move one interviewer and the whole panel has to re-coordinate. Meanwhile reminders are the first thing dropped on a busy day, and no-shows are how you find out they got dropped.
Add it up and the cost was never really the coordinator's hours. It is the empty chair you already staffed, the crew idling between jobs, and a calendar that only works because one person carries the whole thing in their head. Take that person's Friday off and you see exactly how fragile it was.