Placebo controlled trials are needed for clinical trials and they are ethical. As humans, we tend to overthink and overanalyze situations when it is not needed. Most of the placebo trials are done because we feel that medication will help us when we take the pill. For instance, if we are told we will be given a pill that is supposed to make us more energetic and after taking it you think you feel more energetic. But that pill was a placebo one. Psychology places a huge role in what we feel.
Also placebo pills will act as a control in the trial so it is there so compare results.

https://www.cancer.net/research-and-advocacy/clinical-trials/placebos-cancer-clinical-trials