It's interesting how quickly people are tempted by money. I worked for a store that decided that they needed to reduce staff so they got rid of the supervisors that supervised the cashiers when they cashed out. They figured the cashiers had been there for so many years so they were trustworthy. Almost immediately the cashiers started to cheat by skimming a bit of cash and within a few months, most of them were replaced because they had been caught cheating in some way.
The temptation is too great for many people. Checks and balances always need to be put in place no matter how trustworthy the person is.
This case is a prime example of that.