This has happened a few of times to us. Halfway to the 'specialist' or 'consultant' on a day we have both booked off. (Both needed as the one going to the appointment may not be able to drive back,) So we are 15-25 miles into the journey and the receptionist/assistant rings and says the consultant is unable to see us today due to 'unforeseen circumstances.'
Some consultants are a law unto themselves and really do think the world revolves around them. They think NOTHING of cancelling an appointment on the day if it inconveniences them, or something else comes up. Never mind the fact one (or two if the partner is going) people have taken holiday leave or lost money from having time off, to GO to the appointment! They get paid six figures no matter what, and are clueless and ignorant as to what bother they cause the 'nobodies' like us!
When DH went for an appointment in 2019 to a particular consultant, his appointment was 9.15am. We live 40 miles away, so had to leave at 8am because of the rush hour. 10.45am my DH got in. Only the second appointment in and it was an hour and a half late. Turned out later, that the consultant hadn't even come in til 10am. His first appointment got called in at 10.15am (after said consultant had had a coffee and a chat to his peers,) and came out at 10.30am.
DH didn't get called in for another 15 minutes after that! AN hour and a HALF after his appointment time. No apology or anything! DH came out at 11am, and the receptionist was phoning people due in that afternoon after 2.30om CANCELLING their appointments, due to unforeseen circumstances! The unforeseen circumstances were the Consultant was lacklustre, lazy, sloppy, and was nearly an hour late getting in!!! And THEN didn't see anyone for another fifteen minutes!!!
So whilst there ARE people who CBA to turn up, there IS another side to it all. Many of the specialists and consultants and hospital staff are at fault too sometimes.