From what I can see banks basically have to do two things :
1) Provide savings products and a prudent lending service which gives customers and businesses access to finances and the bank makes a tidy profit and not run the bank into a wall requiring a massive government bailout to prevent the collapse of the economy.
2) Run a reliable transaction system that supports day-to-day personal and business transactions.
RBS fails on both of those counts so, one would have to ask : Why is it still in banking!?
This is pretty fundamental stuff!
Their Ulster Bank subsidiary over here which operates in Northern Ireland and is also one of the largest consumer banks in the Republic of Ireland suffers these IT glitches too as their IT platform was centralised back to RBS HQ some years ago. (I was with them for a long time before that and there was never any issue!)
When the RBS system went down in 2012, Ulster Bank customers faced nearly 6 weeks of disruption! The RBS and NatWest customers' issues were resolved a lot sooner. It was absolutely unprecedented over here and it really sent a lot of customers running to other banks. I mean can you imagine being without your current account and debit cards for over five weeks?!?!
I'm not sure why the Ulster Bank situation took longer to resolve than RBS and NatWest, but I would speculate that they've merged they may have merged their IT infrastructure, but still all be running quite different software albeit out sourced to a single centre somewhere. So, I'm guessing the IT unit either didn't know how to work Ulster Bank's legacy software or that it failed differently somehow when the glitch happened.
Clearly banks operate in some kind of parallel universe where this kind of stuff can happen and they remain in business thanks to government support.