I agree with you. The problem is some doctors think they know more than do. You are ill. You go to the doctor. They run tests. The tests come back negative (ie

I agree with you. The problem is some doctors think they know more than do. You are ill. You go to the doctor. They run tests. The tests come back negative (ie no evidence of illness). The doctor insists you are not ill. But you know you are. But... new tests are being developed all the time. Maybe in 5 years a test will find that you are ill. But for the 5 years up to that point the doctor will insist you are not ill. A better logical position for the doctor would be "you may be ill, but we can't figure out what it is".