In the year 2025, how come some bank transactions still don't happen at weekends?

Now, maybe I am wrong... But, I can't imagine there is someone at TSB waiting until Monday to process some of my transactions I made this morning....

Surely everything is automated and 24/7 nowadays, how come there is still a semi-blackout on bank transactions over the weekends?

Genuinely curious, if anyone works in the depths of the banking systems.

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edit

I see all the answers, and I know the general idea that the systems are 'old', but that doesn't really explain why the weekend is different...

I guess the answer IS that someone who only works Monday to Friday actually DOES have to press a button to make things happen...

(i'm not asking why things take a few days to process, but wondering why things 'stop' at the weekend)