1. Most big banks require a ton of red tape to use those APIs. Even if you're using modern technology with a top tier dev team, this is still a 4-6 week endeavor at its absolute quickest turnaround.
2. All ACH transfers, for example, have to clear the Fed, which is done via FTP.
3. The consumer use cases are endless (make payments, analytics, etc). Just look at Mint, Truebill, etc.
4. The commercial user cases are endless (treasury management, AP, AR, etc).
(Disclosure: I'm the CEO of Duffel) Totally agree with your point above re: IATA. They made it possible but for a different reason, they opened the door to competition.
Standardisation of communication protocol can only do so much, especially when the standard is built to accommodate the needs of 100s of airlines using 100s of different host systems.
Also, there is ton of red tape around airlines' APIs as well, I'd say probably as much as in banking.
2. All ACH transfers, for example, have to clear the Fed, which is done via FTP.
3. The consumer use cases are endless (make payments, analytics, etc). Just look at Mint, Truebill, etc.
4. The commercial user cases are endless (treasury management, AP, AR, etc).