You are not wrong - placebos are a practical way to blind a study. The best way to blind, however, is no treatment, but no treatment only gives you the efficac

You are not wrong - placebos are a practical way to blind a study. The best way to blind, however, is no treatment, but no treatment only gives you the efficacy of the treatment, and not what you actually want to know, the efficacy of the 'active ingredient'. See e.g. https://en.wikipedia.org/wiki/Placebo-controlled_study#Natural_history_groups https://en.wikipedia.org/wiki/Placebo-controlled_study#Natur...