In the financial sector, vacation is a fraud control. Reshuffling job duties makes it easier for others to discover your misconduct, and temporarily suspending your access makes it harder for you to cover it up.
it would seem this would mostly only work if the vacation was imposed randomly. otherwise you have plenty of time to plan it.
Even limiting the scope to things that can be covered up with some lead time is a benefit.
My mother worked in banking, and was required to take a consecutive two week block of vacation. I believe the idea was that any fishy financial sruff would likely come up during such an extended time off.