The mandatory vacation is there to make sure the employee is well rested, efficient at his job and not incurring extra expenses by becoming prone to illness through overwork. You assume that if there were no mandatory vacation laws your salary would be higher but that is highly unlikely - your taxes would be just as high (and in the long term probably even higher because of the side effects), paying to support social measures that improve the life of all citizens (e.g. - guaranteed healthcare).