Why do health care professionals have new patients fill out a medical history?

The questions on those medical history forms contain some very important information. Much of it is about chronic conditions that the patient may have.

Patients usually come to the doctor to get treated for a specific problem they are having at that moment, but they may not realize how it is connected to a problem they have been having for a long time. Or it may be connected to things that the patient doesn't even realize are problems.

The patient histories also give the doctor a clue as to the general health of the patient and lots of the family history, since many conditions passed through families.