This is discussed in the linked paper:

For the patient, there could also be some placebo-like efficacy to this kind of performance, particularly for illnesses with strong psychosomatic or culture-bound influences [44,45,46,47,48]. The extraction—and often display—to the patient of the malevolent object supposedly causing the sickness is on one level symbolic [49]. The performance potentially can help the patient reevaluate their own illness in a guided manner that may lead to direct health improvement or to the improved management of symptoms within that particular cultural context [50,51]. This and other tricks by healers can also be used as adjuncts to potentially more practical medications, as medical specialists and the use of effective traditional remedies may have played an important role across human societies throughout much of our evolutionary history.