We have not had any replies from people whose work is by appointments. It would be interesting to see what their opinion is.
How many missed appointments make a difference to the viability of a business? One a day? Two a day? Five a day? Ten a day?
It depends how long each is for and what the cost of providing that service is - and what the difference is between costs and takings. If it is a little local hairdressers, their charges might not be very mush above their costs, so missing, say, two lots of charges out of twenty in a day would mean losing ten percent of that day's takings. If their margins are ten percent, (no idea whether that is common) that means a day with no income at all!
A prestigious West End salon could have much higher margins and be more able to absorb the fall - but they are also in a much better position to demand and get attendance at all appointments, so they are not so likely to be badly affected.
Would anyone be pleased if their boss said they would not be paid for one hour of their work today because there would be no customers there then?