What are we all filling out those forms before the visit for if the doctor's not even going to read them before we see them?

A doctor is supposed to do an anamnesis each time it might have some consequences. This is not because they are stupid, or thing you are. People simply have error rates. Just because he wants to hear everything again from the beginning, does not mean he hasn't read your file. He want's to make sure, nothing got lost or forgotten including by the patient himself. And he is actually supposed to do so, if he doesn't that's bad practice.