Yes, salaried employees in Korea should be given three weeks of paid holiday in addition to all national holidays because doing so would certainly be great for morale. Employees who feel happy, rested, and wanted are productive employees, and thought it may seem backwards, giving this extra vacation time would help quite a bit.
While this is great for salaried employees, I would love to see it expanded to cover all employees. Korean employees are very hard working and we have created one of the largest and most modern economies in the world, starting from almost nothing 30 years ago. We should be rewarded for our efforts and loyalty with this holiday time.