This answer nails it. People are terrified, literally terrified of being taken off their dentist's books, and this is why people will often turn up anyway, even if they're not feeling good. Thing is though @DontWantToGetSick many people will be carrying germs and viruses several days before any symptoms kick in, so you could easily get ill even if you treat someone who appears to be fine. You always wear a mask though, so that should protect you a bit.
I'm sorry you are getting a hard time on this thread, and someone spluttering and coughing should really not come in to see you. It's a bit gross for you. But yeah, people are scared of being taken off their dentist's books. I don't think I have cancelled or missed a dental appointment for a decade and a half now, as even before Covid it was difficult to get an NHS dentist, and I don't want to be booted off!
We have to go to the dentist every six months, but we used to go to the dentist once a year pre 2010, as they never requested 6-monthly. (DH and I, and our 2 DC - then school age used to go.) Life got so hectic at one point (as it does - when you have children, you're running a home, you're looking after elderly parents, and you have a job,) and I realised we hadn't been to the dentist for 2 years and 1 month. (Had the last appointment in a diary.) We went June 2008, and in July 2010 I rang up to book us all in for a checkup. I was told we had been taken off the books. No warning, no reminder letter, or text, or email. We no longer had an NHS dentist. We could not afford private.
Yes I know it was down to us not going for 2 years (and 1 month) but a reminder letter might have been nice. I felt I had let my children down, as they no longer had a dentist. I rang about 12 different dentists, some up to 25-30 miles away, to see if we could register - or at least go on their waiting list. Just one said we could go on their waiting list. NO-ONE had any spaces, and no other dentist would let us go on a waiting list.
It would be a full year before the one dentist rang me and said we can register now, and made an appointment for all 4 of us to register. (This was around August 2011.) Fortunately it was one that was only 9 miles away, and not one that was 30 miles away, although I would have accepted anything to be honest, just to be registered.
We moved area about 2 years later, (moved 30-ish miles away,) and put our name on the list of a dentist just 3 miles from where we live now, as our old one was now 33 miles away, and obviously having one closer is better. But we had to keep going to the old one 33 miles away for about 18 months before we could get registered in the one in our little market town. (And they required 6 monthly, and we had to go 3 or 4 extra times for emergency treatment.) Again, with our new dentist 3 miles away, we never miss an appointment. Fortunately, we have never been ill when we go though.
I didn't realise you didn't get paid when people don't turn up @DontWantToGetSick I am sorry to hear that, I really am. I genuinely thought you did.