"Specialist Clinic wait times"

I don’t understand why appointment times are made if seemingly no attempt is going to be made to meet those time frames. I believe patients should at be warned at the time of booking that they do not have an actual appointment time and that they should expect a significant wait beyond their required arrival time. 10am appointment. Told to arrive at 9:45am to register. Not seen until 11:45! Someone explain to me how this booking system works?