[advisedwang]

If I sell my couch for paper money to a someone that got that money through a crime or in violation of a sanction, I don't realistically have to worry that someone could try and claw back that money from me by tracking the payment.

Paper money has serial numbers, but likely nobody record them during the criminal transactions. Even if they KNOW which serial numbers are involved in a crime (maybe they robbed the mint), there's no database that tells them I have that note now and no infrastructure to catch someone from spending it.

(Of course perhaps the money is clawed back because there's text messages on the criminal's phones about buying the couch. But that's another story)