I'm curious if any companies have required (minimum) amounts of vacation. Taking a break seems to be a general positive for productivity, but people with unlimited vacation seem to not take it. What if you were obligated to?
Required vacation time is a security best practice, especially for anyone handling money. This makes it more difficult to perpetrate fraud. It also prevents institutional knowledge from being trapped with individuals, as at least one other person must know how to perform the role of the vacationee.
Say you're a bank employee who handles money. It'd be pretty easy to just slip some off the top of each stack every day and take it home. Or arrange the software to skim some into a separate account and pull that money out often enough that the balance never gets high enough to be suspicious.
Both of those things, plus many more, require daily or weekly effort. If you're out of the office, something will go amiss and you'll get caught.
It's fairly commonplace in the federal government to have 'use it or lose it' leave. Only a certain amount of vacation hours can roll over from one year to the next, so those which you don't use and don't roll over are lost.
While it's not mandatory to take that leave, it's a very good excuse for why you want to take several days off.
Most jurisdictions require a certain number of days out of the office for people who work in finance. In Japan, it's ten consecutive business days each year. In the US I believe it's five.
