That's what you get with Free Services. If it doesn't cost you anything to miss it, then you do not consider the consequences.
It's the same with restaurants, Those that do not require a deposit for bookings are subject to plenty of 'no-shows' which affects thier takings and puts their survival in jeopardy.
It's pure selfishness and incredibly inconsiderate. In the case of the Restaurant it's putting livelihoods in jeopardy, but in the case of the NHS it's putting people's lives at risk.
I'd welcome a Fines for those that don't turn up for appointments.