The cause of back pain in many patients is unknown. Even with many tests and many opinions, it can remain a mystery. That's why you can see five trained professionals and get five different answers.
Most diseases and illnesses are treated on the basis of what's causing them. Back pain is more often treated based on the patient's signs and symptoms. Each health care worker views those symptoms through a bias based on his or her own training.
It's more than likely that all the opinions help piece together the whole picture.