CS
While it may only be a lost weekend for everyone a very large number are inevitably mis-employed the preceding week setting up and some the following week.
Then for a fair number their primary job goes on the back burner for days, weeks and even longer.
If you are established at 100%, manned at some level below that, then your effective manning will drop below operationally effective levels. We had one air show at Waddo cancelled (while Finningley was still going) when operations intruded.
It was cancelled sufficiently early that we didn't incur a big loss but if there is a late cancellation who picks up the bill?