Self-assessed health is also a strong predictor of functional limitations (what you can and can't do). The doctor considers it a red flag anytime a patient chooses poor to describe his or her overall health. Your chances of a good recovery with treatment are less than if you graded your health as good-to-excellent.
Doctors may use this information to decide what's the best treatment for each patient. They may also take a look at the big picture for all their patients combined together. They may look to see what can be done to improve health for everyone.
Patient education programs are often planned based on what patients' needs are. Surveys of this type may help bring this kind of information to light.