Digital currencies don't enforce any policy other than avoiding double-spending. (Set aside smart contracts for now.)

Other online payment methods (Visa, PayPal, Stripe, your bank's ACH, etc.) do. These policies start by disallowing illegal transactions (crime). Then they disallow unfair transactions (buyer claims not to like the quality of the item, etc.). Then they disallow immoral transactions (gambling, pornography, etc.). Then they disallow anything... unseemly? (2022 Freedom Convoy protests, Stripe briefly banning certain legal, non-adult LGBTQ+ transactions in 2025, etc.).

Is it a problem that your currency-transfer system enforces policy? Many people don't care, but to some, yes, it is a problem. They don't want PayPal telling them what they can and can't do with their hard-earned money, because that's the job of their government, their religion, and their conscience. They want their online cash to behave like offline cash.

If you were designing a system architecture for value transfer, would your low-level primitives throw policy exceptions, or would you delegate that responsibility higher in the system?