It is very common in Korea and Japan, as well as elsewhere in Asia, for people at home to sit on the floor for studying, relaxing, using the computer, even dining (some restaurants, even fancy ones, also offer floor seating). Such practice is virtually unheard of in Western countries, except among young children.
Is this down to a perception of cleaner floors due to shoes being taken off? Or a lack of room for chairs? Is it a holdover from a nomadic history when transportation of chairs was not easy? Or is it because the chair as an invention was not brought over/commonly seen in the East and this is a holdover? Or some other reason?
I've seen Korean textbooks that give the ondol as a reason, since it's both comfortable for walking without shoes, and warmer to sit on directly, but I have doubts since it's only useful in Winter and often somewhat small. It's more likely the multi-purpose use of each room, with sleeping and sitting furniture being moved in and out each day and stored in chests and so on when not in use. Each item has to be fairly small for this reason, and chairs and tables would be both heavy to move and impossible to get out of the way for sleeping.