A centralised system with trusted nodes is far better for transaction times - this is the worst use-case for a distributed ledger. Blockchains try to avoid trusted nodes, and thus their transactions are slower, because they are multi-node, by design.
Banks already provide transfers in seconds (perhaps not in your country).
Banks make money because clients trust them, they are insured, provide reversible transactions etc, not because their transactions are slow.
The reasons for why settlements take days, and not seconds, is procedural, not technical. If the financial world wanted instant settlements, we would have had them decades ago.
The financial world optimizes for intent and compliance, not speed. This is why settlements take days, and why cryptocoins aren't very interesting to it.
Transferring money from one account to another account is as simple as updating two rows in a database. That the database is not a distributed proof-of-work ledger has nothing to do with it taking days.
As a confirmation - they wanted it and they have it: https://en.wikipedia.org/wiki/Single_Euro_Payments_Area#SEPA...
In my country there's a scam where people find out you're buying a house through a particular solicitor with a large cash transfer, then they send you an email or even a physical letter saying there's a problem, the solicitor just found out their firm got a new bank, or whatever, please transfer the house money to the new account. Of course it's a lot of money so most people will want to check this is right - they provide their phone number on the message. This number, of course, is part of the scam and a "secretary" will answer saying your solicitor is busy right now, but yes, they're very sorry, the message is genuine and please use the new account details.
The large sums involved mean this scam is very lucrative even if it doesn't work on say, 99% of potential victims.
If the victim realises they've been scammed ten minutes after the transfer, chances are good the bank can fix it, because settlements aren't really instant. If they realise the next day, or two, or three days later, the money is gone. It went to a mule, who has already forwarded it, the police might arrest the mule if they can find them, but the mule doesn't have your money, they're just another sucker.
Already happening.
SEPA Instant is either being released or in trial phases. My bank is trialing it, a <10 second transaction costs 1€ fee flat, normal SEPA is still free.
And banks offer me more in terms of personal security. If I lose my debit card, I get all damages reimbursed. If the bank gets hacked, there is insurance.
Unless I fuck it up myself, I'm going to be saved by the bank.
On the other hand, on Bitcoin I can fuck it up myself but if someone else fucks me up then I'm SOL and can go eat ham for all that Bitcoin cares.
For the average users the question of using Bitcoin has become irrelevant with SEPA Inst. Banks are faster with it and offer more features.
Here in India, we have a thing called IMPS. You can send money instantly from one account to another. Transaction cost is a flat Rs. 5 (less than $0.10) for any transaction size.
There are other newer protocols as well such as UPI which I haven't really used because IMPS serves my needs perfectly.
Sending money to another account is basically a non-issue here.
And tbh, the banking situation in the US is just amazingly bad. Horrifyingly bad if I believe the more out-there stories I hear from people.
The only time I got charged a fee was for a transaction into the US (the fee was currency exchange fee and nothing else). And the fee was seperate so the transaction amount was unchanged.
Yet in the US it seems possible that banks will take a piece of a transaction for themselves.
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In search of a solution to a problem nobody but the US had, we have blockchain now.
At one time I used to get paid from a US employer's Bank of America account. I also had an account in the same bank, but transferring the money between our accounts in the same bank took 3 days. I presume due to some split between business/personal banking, but still absolutely ridiculous. We switched to sending the payments to my European account through SWIFT, and those payments happened same-day.
E.g. debit from Bob's account on Monday, put in <money market/whatever> from Monday until Thursday, and then put it Alice's account on Friday.
This is only a problem in the USA. By contrast, in Britain, the Faster Payments Service (https://en.wikipedia.org/wiki/Faster_Payments_Service) has provided transfers within a few minutes for more than 10 years now.
You manifestly do not need a "blockchain" to solve that problem.
But long term, banks will need to accept faster transaction times. Blockchain or not, it's ridiculous you need to wait days to transfer money when you can send email in milliseconds.
Rather than accept Bitcoin, it's far more likely big-banks will get together and form their own crypto coin, which will enable faster transfers, but keep them in control. They'll get regulations passed that will make Bitcoin and most other crypto currencies illegal or legally risky, whereas their system will be blessed by regulators.
Under this scenario (I think the likeliest), the existing power hegemony stays this same, crypto-currency's idealistic roots become viewed as naive and antiquated, and consumers get slightly faster transfers through their same old banks with marginally lower transaction fees.