When a bank starts up, it have a simple system. Which requires x amoint of people to maintain.
Over time it is discovered that this system only offer functions A, B, C and D.
And it needs extra systems to offer extra functions. So these got added duly.
Unfortunately said new systems also needs its own maintenance, so therefore extra people.
Which brings us to the here and the now. People have forgotten why there are so many people requires in order to maintain the system, and is lured by the outsourcing siren, and start outsourcing.
Now systems are failing, people don't know why, the outsourcer(s) don't give a damn about your SLA... and the people who have an intimate knowledge how the system works have been chased away, never to return.
Biting the hand that feeds IT
