This reminds of the abandoned practice of women being prescribed Hormone Replacement Therapy (HRT) for menopause. Essentially the reasoning was "why not, it seems to improve patient health and we don't see any ill effects". It was such common sense at the time that it took over 30 years before a clinical trial was performed. That trial demonstrated a much higher rate of breast cancer and heart disease in HRT patients.

The NY Times has a good write-up on it and more generally the challenges with epidemiology and causal analysis in medicine. https://www.nytimes.com/2007/09/16/magazine/16epidemiology-t...