These are actually a benefit the the employer. Issuing official paid time off amounts to additional compensation to the employee. If you have 3 weeks of paid vacation available, that shows up on the company's books as a liability that has to be accounted for on their balance sheet. So, you are in effect being paid your salary + however many days off you get. I'm not sure how it works with an open door policy, but I suspect they'd be able to assume a smaller liability based on the actual number of days people take off rather than some amount that they're owed.