It's not purely Confucian — a specific colonial-era mechanism gets less attention than it should
FACTConfucian social philosophy, dominant in Korea from the Joseon dynasty onward, does establish elder-younger as one of its core Five Relationships, and provides the deepest philosophical layer for age-based deference in Korean culture.
FACTSeoul National University of Education professor Oh Sung-cheol has published research arguing the modern rigidity — where even a single year of age difference dictates speech patterns and forms of address — didn't come purely from Confucianism. He points to Joseon-era scholars who formed close friendships across large age gaps based on shared intellectual interests rather than age, and instead traces the strict, uniform hierarchy to Japan's colonial-era school system (1910-1945), which imported military-style strict senior/junior submission structures directly into education — a hierarchy students then carried into adult institutional life.
FACTBroader academic consensus treats this as multi-causal rather than single-cause: Confucian hierarchical philosophy, colonial-era institutional militarization, and the collectivist organizational culture reinforced through the Korean War, the Cold War, military dictatorship-era governance, and state-led rapid industrialization all layered onto each other across the 20th century.
INFERENCEBecause the system has this many independent reinforcing layers, removing any single one of them (say, updating school discipline norms) wouldn't be expected to dissolve the broader hierarchy on its own — which is consistent with how slowly this culture has actually shifted despite decades of formal modernization elsewhere in Korean institutions.