Up until 1985 or so, a lot of "experts" thought that pumping piles of corticosteroids into a bulged disc or inflamed knee was helpful. Then modern science continued to make discoveries for the past 35 years. Unfortunately, the American Medical Association didn't get clued in until recently: https://jamanetwork.com/journals/jama/fullarticle/2626573
But the oddity is that the mechanism of steroid injections was always understood. We knew that they turn off the growth factor cascades which repair tissue. That IS their mechanism. A brief run-through on PubMed, and you'll discover that studies already defined the degenerative role of steroids as far back as the 1960s and 1970s: https://www.ncbi.nlm.nih.gov/pubmed/5808578
So, why did it take over 50 years for the general populace to become aware of a fully-understood and detrimental procedure? It's a great question without a solid answer, because most people still don't know this. I've even run into clinicians who don't know this, still believing that pro-inflammatory procedures are quackery, and that the archaic steroidal injections are the way, the truth, and the life.
Perhaps it has something to do with our immediate-gratification culture. People like to "feel" better in the short-term even when it's obviously destructive in the long-term. Either way, if you encounter people whose beliefs of steroid injections hearken to the 1950s, try to spread the news. It may be a shocker, but we have been continuing to conduct science for the past 80 years. Time to update.