Your post brings to mind an article by (I think) Ben Goldacre in which he recounts that inserting a stent to "solve" narrowing of the arteries has never been shown to be a net benefit to the average patient (except for emergency cases).
Nevertheless, cardiologists have continued to carry out operations to insert "new! improved!" stents which successively claim to eliminate the problems of previous designs over what is now something like three decades of medical practice. None of them have worked.
I'll try and find the article, but a quick web search hasn't turned it up.
This was originally unknown and non-obvious (massively narrowed coronary arteries are ok?) but now known and modern clinical guidelines (which are written by physicians) have changed to reflect this reality. This was confirmed by well controlled multi-center trials. It's not cardiologists inserting "new! improved!" stents for the thrill of it.
This doesn't reflect the case of the example patient who has angina upon exercise with significant stenosis, but is not undergoing an active MI. That patient may still be stented and have their lifestyle improved drastically, despite there not being an urgent requirement.
It's not that it was unknown and non-obvious - it's that as each successive stent was shown not be an effective treatment, cardiologists continued to operate for decades, confident that the next "new! improved!" version would work, even though none of the previous ones had.
The reasons for this are a combination of the difficulty of publishing neutral or negative results & surgeons' entirely natural inclination to do something rather than nothing, even if nothing is actually the right thing to do, because operating is what they've trained their entire lives to do.
The same thing happened with extreme chemotherapy followed by bone marrow transplant as treatment for many cancers in the 80s: something like a $billion was wasted on treatments that didn't work. The reasons why it took so long to demonstrate that that particular treatment was ineffective were not entirely the same - read "The Emperor of All Maladies" for the details - but shared the optimism of doctors & patients combined with a plausible theory, which is what ultimately makes for a potentially toxic combination.
Nevertheless, cardiologists have continued to carry out operations to insert "new! improved!" stents which successively claim to eliminate the problems of previous designs over what is now something like three decades of medical practice. None of them have worked.
I'll try and find the article, but a quick web search hasn't turned it up.