answer:Doctors factor in a small window for each patient. Any surprises in a visit can throw the schedule off. It could be someone complaining of an ache but in the office it is evidence of a cardiac problem, or another critical issue. And, they may get interrupted with an emergency. My father went in last minute to see about his breathing, next thing you know an ambulance took him to intensive care. We cut Doctors slack because they work long hours and weekends caring for people.