The article points out the primary source is recycling operations.
This is not some big currency or export program. It's most likely Grandma and Grandpa hawking their jewelry.
The cash for gold industry in the US is absolutely massive and growing. Most of it is fueled by boomers dumping their assets into gold and silver - and then cashing it out when times get worse.
There is a reason Pimps, Dealers bought gold chains versus kept cash. Cash and bank accounts could seized while what your arrested with, such as jewelry, is given back to you upon release.
Need cash on hand, pawn it or use it as collateral for a loan.
It is away around the legal system to retain wealth.
Why couldn't jewelry or other items you are arrested with be seized as well if they can prove (or rather, if you can't disprove) they were bought with ill-gotten gains?
I have 30 lbs of gold plated PCB fingers that I have saved over the years. It might be time to figure out how to recycle and sell.
That’s not just a US boomer thing, you’ll see the same in many Arabic countries for example, across generations.