Neither the patient nor the practitioner knows for sure if a new or untested treatment actually works. In fact, the effects can be so strong that negative effects can result. This is called the Nocebo Response. Both the doctor and the patient want things to improve and so, sometimes, they do. Scientists postulate that the placebo effect is the result of mental processes affecting physical events.
Many studies show that placebos are effective against pain.
It may be that a reassuring doctor who offers a treatment may reduce anxiety which in turn relieves the perception of pain. No, it is just another tool in the kit that practitioners use to help their patients. Many people feel better no matter what they are given, but if they have an organic disease they don't get better. That delay in treatment or complete lack of treatment could result in a person dying from a treatable disease. It's vital to differentiate those alternative medicine approaches that function as placebos and those that are truly effective.