> The alternative would be some sort of joint venture between all the banks. The result would less fees for the banks but no benefits for the client as the bank would keep the margin and it would still be a privacy hell.
This is what happens in India. UPI (unified payment interface) was launched by NPCI which is kind of a joint venture between the regulator and banks. In an abstract sense, the bank processing the payment does connect with every other bank via NPCI.
The underlying rails are an older infrastructure of IMPS[1] which is the interbank money transfer system.
I do not agree with the privacy hell part. When bank transfers happen, they anyway have to do the required checks with the other banks. Frankly, people in my circle never even cared if it could be a privacy issue for us.
On another note, there was always incentive to launch NPCI in india because 1/ The infra is relatively newer so it was easier to do (java I think) 2/ Almost all banks' software was built by Infosys/TCS etc. (in java) and that meant the ones integrating would be the same parties who practically used the same architecture 3/ Visa/Mastercard did not have that kind of penetration in 2010 so settlements were a real issue faced by every bank.
In US or European case, the issue seems bigger because the problem is half solved by Visa/Mastercard, so there is a bit of inertia to solve the same problem again.
[1]: https://www.npci.org.in/PDF/npci/upi/Product-Booklet.pdf