you can pressure your employees with your vacation as leverage
Most places start asking for vacation requests a month or two out before schools do theirs. The US definitely keeps a tighter leash on vacation time than Europe. General US sick-time policy is an abomination.
In my industry, the standard is "unlimited" PTO/Sick for salary. You don't have a limit of what you can take, but it has to be OK'd by your manager. They expect you to take at least 4 weeks.
But if you leave, or they let you go, they don't have to pay you for time accrued.