[ytdht]

I was thinking that they added this delay so that they could profit from everyones money for a few days, continuously.

[jslampe]

This used to be a big thing, but since Check 21 and truncation that amount of money banks made has been severely marginalized. The big reason stems for risk.

The 2-3 allows the receiving FI to mitigate, IIRC, around 70% of the risk associated with the most popular types of rejects. (e.g. insufficient funds)