> Because UPI is designed to be intermediated by computers rather than by humans, transactional information gets captured by the payments company while the transaction is in progress, and that can tell the clerk (or cron job) that the payment succeeded without them needing access to the bank account.
> This is a fun engineering challenge in many countries, which are often overlaying bank transfers as a payment method on top of bank transfers as a settlement method.
[…]
> Bank transfers are an extremely small percentage of customer-to-business payments in the U.S. In addition to the speed issue, which might get improved by FedNow when it launches (wags have referred to it as FedLater), bank payments have no consistent way to receive metadata, and despite being no-cost they compete with well-developed credit card ecosystems which credibly offer better-than-free pricing through rewards schemes (to the customer, who generally gets to choose which payment method they use to transact).
https://www.bitsaboutmoney.com/archive/bank-transfers-as-a-p...