"What is the point of appointment times?"

I was asked to attend with a full bladder for a transabdominal ultrasound, and of course, I was there at the right time for my appointment. I’m assuming it might have been one of the first ones in the morning. 

My bladder was indeed uncomfortably full, but finally was taken from one waiting room 15 mins late to sit in another for a further 15 mins. Normally I don’t bother too much about these things but it was very clear that the staff were there and ready for the (now overdue) appointment.

What was the point in me turning up for my appointment time if the staff can’t stick to theirs?  Like I say, I understand appointment times will slip through the day. These things happen. But this was clearly one of, if not the first appointment of the day. 

I feel it would have  been received quite differently if I had sauntered in half an hour later.