This is one of those areas where anecdotes can be quite valuable, because there seems to be no real downside risk to a piercing aside from the money spent and possible infection, but if there's even a .01% chance it could stop debilitating chronic pain, then sure, you might make a valid decision to try it even though there isn't a study supporting it.
I tend to think in medical science that often anecdotes come first, then the "real" science. Not always populist anecdotes / wive's tales / etc, often times they come from nurses, doctors, or researchers of all kinds -- but sometimes they do come from sparse clusters of common folk sharing anecdotes with each other. Most do not pan out.
But the "hard" science generally needs a spark of intuition to help someone decide "maybe I should look into this", whether it's naive citizens positing that a certain practice/diet/supplement seems to help one of their conditions, or doctors noticing a pattern with a handful of their own cases, or researchers noticing something interesting but unexpected in vitro.
Again, most of these anecdotes don't pan out, but many do, and still today often against best-practice medical wisdom for systems we know less about.
The human body is massively complicated, and we're still just dipping our toes in a lot of new frontiers, and there are some areas which are very difficult to formally study.
