Going to the doctor is a lot like submitting a service request to the IT help desk. Even before you see the doctor, you know what disorder they are going to suspect initially and you know that it is not the actual problem and you also know that they will not consider anything else during the initial consultation. The only way to get them to consider any alternative cause for the problem is to go through the motions of testing and treating that initial incorrect diagnosis.
Only when that pointless treatment and analysis has completely failed will they even consider the possibility that there may be another cause for the problem. It is only at this point, and after a lot of wasted time (and money), that investigation into the real cause of the issue will begin.
Just like with the IT help desk.
(My humble apologies to any doctors and IT professionals who read this. My father is a retired doctor and I was an IT professional for 20 years, so I also know what it's like from the other side and I understand why things are done that way. But it's still very frustrating.)