Every problem you solve takes time away from solving other problems, and this one is a particularly difficult coordination problem with very little payoff.
You might be imagining two banks coordinating together, now scrap that and imagine ALL banks coordinating, because you don't know which two are going to merge.
Banks have been born at different times (think centuries - or even millenia). So they'd all have to move in lockstep from clay tablets to papyrus to printing press to typewriter before they even decide whether or not they want to bet on computers as a way forward.
To some degree banks already have 'a shared operating system' in the form of clearing houses and central banks. I don't know enough about that stuff. But it's the reason why bank transfers have mostly taken days to complete, rather than seconds, in the past few decades.
Come to think of it, there's a huge incentive not to stay in lockstep with all the other banks if you can offer customers instantaneous transfers when other banks make you wait for days.
Bank transfers take days to complete because of liquidity management, not due to IT system delays. When you do a big enough transfer, the bank has to have a balance with the central bank that can be moved to the target bank's CB account, but, your bank doesn't actually have the money you deposited. It's out on loan instead. So the bank has to go into the market and sell some assets to raise that money. It may not be possible to do this immediately, and even if it is, they want to be able to time their sales to reduce capital inefficiencies.
This is also why they're often so very expensive. That $25 or whatever isn't being spent on the cost of updating the ledger. It's the cost the bank incurs because of the need to sell assets (loans) before they intended to.
It is, because in some older payment systems all payments go via the same "rails" as they call it.
Specifically, the reason that payments are still tied to the nightly cycle is because orders submitted to the central bank aren't executed immediately. At night they suspend submission of new orders and do something called netout or payment compression on the transfer graph, the goal of which is to reduce the amount of money banks need to hold at the central bank. Every payment no matter how small can contribute to the netout, reducing liquidity needs at the CB.
You might be imagining two banks coordinating together, now scrap that and imagine ALL banks coordinating, because you don't know which two are going to merge.
Banks have been born at different times (think centuries - or even millenia). So they'd all have to move in lockstep from clay tablets to papyrus to printing press to typewriter before they even decide whether or not they want to bet on computers as a way forward.
To some degree banks already have 'a shared operating system' in the form of clearing houses and central banks. I don't know enough about that stuff. But it's the reason why bank transfers have mostly taken days to complete, rather than seconds, in the past few decades.
Come to think of it, there's a huge incentive not to stay in lockstep with all the other banks if you can offer customers instantaneous transfers when other banks make you wait for days.