Most comments here are only focusing on medical devices; this is about the practice of medicine, not shitty companies! In dentistry/endodontics it was believed

Most comments here are only focusing on medical devices; this is about the practice of medicine, not shitty companies! In dentistry/endodontics it was believed for a long time that installing a post helped keep a crown and tooth intact for longer. But long term studies showed posts can actually reduce longevity. In another case, a study showed that a common type of knee surgery for pain is actually less helpful than a placebo surgery. The overarching problem is that it's (currently) very hard to evaluate the real effect of practicing medicine on large swaths of the population, and then using those results to change what doctors do. By getting doctors into a continuous improvement cycle, we could identify costly, useless practices, and improve health.