Because most scientists, doctors and public intellectuals have never been trained in proper epistemology––the study of the origin of information and how to appraise the truth--they consistently make inaccurate conclusions from “studies”. In fact, they live in a constant state of nihilistic epistemic anxiety where a “new study” can overturn their entire paradigms for understanding the world around them.
They have no mental models for how the world functions and no epistemic principles through which they can evaluate “new data”. Therefore, they never actually “learn new things” they are just easily manipulable talking heads that will repeat the conclusions of those with the deepest pockets to fund the newest study on why eating bugs is good and going back and forth as nauseum to ask “is coffee good for you?”