Comment by Otterly99

They do work to some extent. If doctors wanted to be thorough*, they would use two control groups. A placebo and a "don't do anything" group. Since the placebo effect is known to reduce pain, it is not ethical to not at least administer the minimum of care (which is still like a magic band-aid, but it helps alleviate pain and in some rare circumstances, symptoms) .

edit: through->thorough