Swami Chinmayananda’s answer to why does a realized person work?
When one realizes the Truth, one becomes irresistibly vibrant with life. In divine spontaneity, activity gurgles through him. The physical equipment is generally too frail a reed to stand the blazing gush of love and work; therefore, such prophetic masters generally fold up in a blinding flash of brilliant service to mankind, carried on for a short duration of perhaps twenty or thirty years.
Your question is, “Why should he work?” Can you tell me why the Sun is illumining everything around it? Why fire is hot? Sugar sweet? Oceanic waters salty? Why birds fly? Flowers bloom? Mirrors reflect? Air moves? Earth revolves?… Are they not expressing their essential nature? Can any one of them remain without their essential property? The realized saint is not responsible for what he is doing. He is one with Life. And Life expresses itself in action.