[tsimionescu]

You are conflating two things: medical research and the practice of medicine. During the normal practice of medicine, most doctors do everything they can to harness the power of the placebo effect: they reassure the patient, they speak calmly and warmly, they encourage religious people to pray, etc. Doctors care about a positive outcome, and will take any help they can get to achieve it.

In medical research, we are interested in figuring out if a particular drug helps for a particular condition. We already know that for some conditions, even giving patients a drink of water helps a bit. We need to understand if the drug is better than that, or if it only appears to help. The placebo effect is a baseline of noise in this case, and we need some way to filter it out to understand if there is some signal from the drug itself. If not, then you might as well give the patients some water rather than waste their money on an expensive hard to reproduce potentially poisonous substance.