[loudtieblahblah]

same reason we believe observational studies in nutrition, or worse - studies on animals.

if you have the weight of peer review or at least a well documented study, then the media runs wild with it's claims, it gets shoved into textbooks, then governments shape policy on those claims, corporations and medical practices sell gimmicks, books, supplements, therapy and plans of action to heal you... it all becomes lies, half-truths, bad data all just repeating itself ad naseum until "truth" is established in the public consciousness. Quacks on the web, the American Heart Association, your local doctor's office will all pedal garbage based on the bad data. And once it's well established as true, backing away from it is hard because it's become so woven, institutionally.

This is why people think saturated fat and sunlight are bad or at least a net-negative.

Even modern medicine, psychology and nutrition sciences all have horrible replication crisis's and we're no better in rejecting the nonsense now than we were then.