Classic property of medical science. The science of trials and errors. We know what works, under which conditions and doses and what side effects it may have. Thats useful, important and urgent with real consequences.

The "why" costs money, resources and an itch for genuine curiosity and ingenuity with mostly negative returns. So it remains unknown, while we focus on the combining 2 or more things we already know and see where that can be sold.

Another observation here is there's a lot of money riding on "pseudo science". See any superfood or beauty products for example. You take a data point that is demonstrated under certain conditions in a controlled environment. Make that single data point a centerpiece of evidence, tack the usual goop on it, market it, label it and place it on the front aisles of Trader Joe's. Now there's a lot of incentive to keep the "why" away from consumers walking those aisles.