From a fraud perspective, the point is that a consecutive 2 week vacation is enough that someone probably needs to take over your financial roles, so it would become obvious to the newcomer that you're committing fraud. An example of a type of fraud this could expose (or prevent happening in the first place) is "kiting", where you steal a payment from a customer, then apply over customer's payments to that payment, then apply other customer's payments to those misallocated payments, etc. Doing this prevents those who look at the accounts receivable summary from seeing that payments from Company X have been outstanding for a significant amount of time. Making sure someone takes a vacation makes this much harder to do since someone else will be looking closely at your work in the meantime.