Why do they work harder?

edition.cnn.com

Not only South Koreans but also most of the East Asian people believe "Endeavor must contribute to richer life."
As a means of showing endeavor, they try to work harder. In some cases, they work harder to death.
Especially in South Korea and Japan, devoting to their bosses and companies is also taken as an important role to get the hang of the company life.
Whether or not they actually contribute to their companies, it will be an important attitude for them to show how they devote to their companies.
Needless to say, devotion is often embodied by overtime work.