And why is it not standard practice to provide anonymous data or even publish the data? What reason exists for that? So that only the researchers them selves can analyze it?
Unfortunately it's not easy to see what the alternatives are, beyond simply not funding research through government/foundation grants. When science is paid for by companies you don't have this incentive issue because the research is judged based on (ultimately) whether it leads to successful products, not whether it leads to lots of papers getting published. You have other incentive issues of course.
I'm not a clinician and don't deal with them regularly, but the impression I get is that new studies are published by researchers who have a lot of connections (dubbed thought leaders). They present at conferences. Other clinicians pick up the use case that matches their need (this patient has failed other therapies for this indication, let's try this new thing I'm now aware of). Then as experience grows, clinicians have more nuanced understanding of the use cases for that new information and its reliability. Frustratingly, this can take years, but that's bug that's also a feature.
> In 2016, the International Committee of Medical Journal Editors (ICMJE), an influential body that sets policy for many major medical titles, had proposed requiring mandatory data-sharing from RCTs. But it got pushback — including over perceived risks to the privacy of trial participants who might not have consented to their data being shared, and the availability of resources for archiving the data. As a result, in the latest update to its guidance, in 2017, it settled for merely encouraging data sharing and requiring statements about whether and where data would be shared.