I believe different states have different laws, but at least in my state an employer is required to pay you for your accrued PTO when you leave the company. Therefore, they have to have (and accurately track) PTO on their accounting books.

Years ago, the company I work for switched from accrued to unlimited PTO at the end of the fiscal year in order to make the books look better. When it was announced, they basically told everyone to take the remainder of the month off. The fiscal year happened to be the same as the calendar year, so most people were taking huge chunks of time off due to the holidays anyway and didn't really care. For those who had more PTO than what was left, they were told to work with their managers to arrange for as much time off as they felt was necessary in compensation.

This only worked because it was a one-time deal and the managers were (and mostly still are) very reasonable and supportive people. A while later we were merged with another company and they switched us back to regular PTO to be in line with their own HT policies.