That's sort of the point, I think. It's like buying an index tracker in the underground economy.
now it's way easier to track public blockchain transaction chains on Bitcoin, Ethereum and the like than it is to track bank transfers across countries
Bank transfers are A) linked to a passport and B) can be blocked.
It’s not that hard to cover your tracks. And sometimes it doesn’t matter if your beyond the reach of the authorities in the country the crimes were committed.