In Seoul in the late 90s I paid some $50K equivalent jeonse for a ~1000 sqft apt, with no further monthly rent. From what I understood, the landlord can make back something equivalent to rent via common interest rates. I was young and frankly didn't understand the exposure or workings at play in this article.

Historically, in Korean culture it was very common for the extended family to live together. When a child married they often continued to reside with the parents/in-laws until they had saved enough money to move out on their own. Jeonse is far less than the amount required to buy a place, and because they get the full amount back when they move out to a bigger/nicer place (more jeonse), they can build up their savings until they have enough to buy a place.

Back then mortgages were rather rare and even monthly rents weren't that common. Things are far different now of course.