As others have said, there's a lot of good reasons why and it happens everywhere. That's why when I go to the doctor I just expect I'm going to have to wait and consider it part of the process. Then if I do get in on time and seen quickly, I am pleasantly surprised and it makes my day.

It just happens, not necessarily because a schedule is overbooked but prior patients can be late or their condition is severe enough to take up more of the drs time. You have to choose between seeing a dr that can work you in within a few days and waiting for a little while or seeing a dr that takes months to get in with that sees less patients. But with specialty clinics like cardiology and neurology we can’t really turn away patients therefore most have to wait.