How long should you be kept waiting for your doctor?

The last time I needed to see my doctor, I was given a 10am appointment. As usual I was there a 9:30, there were maybe 8 patients there when I arrived, but most of them were there for blood tests,so they weren't there to see the doctors. I mean I understand that being given a 10 app. does not mean it can't be delayed a half hour, but not almost 3 hours! my doctor finally saw me at 12:45. It's not the first time either,I take care of my elderly father 88 years old, my doctor knows it, but besides this its very frustrating having to wait so long for an appointment I had non the less have to make a month before. What is the point of having an appointment?and why do people think that others peoples time has no value?in those 3 hours of waiting I could have done so many things, mean while I had to sit there like a punishment for 3 hours, I felt so frustrated that I just started crying because I just can't stand injustice,she [ my doctor ] said it was not her fault and left, but sent a nurse in to check my pulse which infuriated me even more.Now I just dread the idea of having to see my doctor, to get my medications.