This is the reality. A doctor is trying to see as many patients as possible who want to be seen. Not every condition requires the same amount of time. They do their best to estimate, but ultimately, if a doctor is willing to give you extra time, then the price is usually paying it forward by waiting longer in the waiting room for fellow patients. If you're late when they are ready, then you drop the efficiency of the entire day. If you're ready when they're not, well, yes, their time is actually more valuable in this case.