Yeah, that’s the thing with placebo. It’s surprisingly effective, and separating the psychological effect from actual chemistry can be very tricky. If most participants can correctly identify if they’re bing fed the real drug or a placebo, it makes it impossible to figure out how much each effect contributes to the end result. Ideally, you would only use effective medicine that does not need the placebo effect to actually work.
Imagine, if all medicine had lots of placebo effect in them. How would you treat patients who are in a coma or otherwise unconscious?