It's about your own sanity! We can appreciate sometimes things happen and they get behind but a better way of management is being informed when you arrive that they are running behind, whatever approximate time is, you can then head off and return or ask if you can jump the queue and see what they say!
When we book in for our appointment there's a screen to book in and it tells you whether you are next or second in line ...
My GP has always encouraged me to let the staff know if I am in trouble and he will see me! Hopefully this hiccup was a one off and your next appointment is on time!