The only thing you have done is emphasize the need to answer his question. When he does an inter-bank transfer, why does it take 3 days for to clear?
I did something similar a few days ago, and while it didn't take 3 days, it did take over a day.
I did something similar a few days ago, and while it didn't take 3 days, it did take over a day.
They chose the cheap, safe option over the fast, risky one. I talked about the difference between net and real-time gross settlement in an earlier comment [1]. TL; DR There is a fundamental trade-off between mutability, speed and cost.
This is not a technology problem. Blockchain won't change either of these.