I hate to overly simplify things, but it's a problem of incentives:
Interventionalists get paid to perform interventions. Let's be generous and say that they have more than one size of hammer in their toolbox; still, every problem looks like a nail.
Patients want interventions, and they don't have to pay for them. Some like them because it proves to naysayers in their social groups that the pain isn't all in their head, that they don't have just run-of-the-mill back pain. After all, if a doctor "sees something on imaging" then it's real. Some like interventions because they help their disability case or their lawsuits. Some agree to interventions because they think that undergoing interventions will lead to opiate prescriptions. Some like interventions because they get out of the house, get doped up on versed/fentanyl/propofol, get attention from cute young nurses, and now have doctor's orders to go home and do nothing at all--so there should be no surprise that they feel mildly better the next day.
ASCs and hospitals love interventions because the checks clear.
I don't think that all pain interventions are snake oil, but I do think that something like 90% probably are. What a fantastic scam, though: target something that everybody at one time or another will experience, that can't be objectively measured, that in the vast, vast, vast majority of times will resolve on its own. In the cases when your interventions have bought enough time for the pain to run its course, you take all the credit. In the cases where the pain persists, you check your list of handsomely-compensated interventions, and suggest something more expensive. Rinse and repeat. And, when you run out of tricks and the patient is still in pain, you simply shrug your shoulders and point out that there's a new sucker in your waiting room, so you'll be moving on.
I'm reminded of the words of Upton Sinclair:
“It is difficult to get a man to understand something, when his salary depends on his not understanding it.”