It is a contractual condition in my firm that all employees must have a least one holiday of two weeks duration every year.
The reason being that in that two weeks a problem might arise that the employee has been hiding (we had a situation a couple of years ago where an employee who hadn't taken a significant holiday for two or three years became ill and had a month off - we covered her work but it like opening a Pandoras box, she was a hider - she'd hide things that were difficult, she'd fabricate, cheat and lie, it was a bloody nightmare).