Unlimited vacation comes down to placing the burden of taking time off on the employee. It's mostly there to deter employees from taking time off and to keep a competitive environment. "X left for 30 days last year, Y only 15. Y seems to be more invested in their work."
Don't let this fool you, it's more often a trap than it's not.
Don't let this fool you, it's more often a trap than it's not.