I expect it’s path-dependent legacy practices more than anything else. Credit cards were invented in the US, so the tech is old and upgrades take a long time.
For manual payments, UPI in India sounds pretty great. Apparently the customer approves each payment on their phone before it goes through?
Credit card networks are already quasi-governmental agencies who block payments the government doesn't like (see e.g. operation choke point) - but without any of the accountability of an actual government agency. Having the processor be the actual government subject to FOIA, equal protection clause etc. would be a step up.
It may be a terrible thing but it has brought such a big change to the Indian economy. Imagine doing that in US which is a much smaller population and all you get is "choice" aka "freedom" to pay 3-5% credit card fee per transaction.
I'll take 3% over having a single payment processor I can't swap out.
The change to the Indian economy was going to come through private investment anyway but the government blocked that. So saying the change came because of UPI is disingenuous at best because it never had to compete with any other offerings. No other entity was even allowed to compete.
For manual payments, UPI in India sounds pretty great. Apparently the customer approves each payment on their phone before it goes through?