What is gained by learning Vipassana meditation in long retreats?

My understanding of S.N. Goenka's method for learning Vipassana meditation is that the student is introduced to meditation in a 10 day retreat in which he or she sits in silent meditation for almost all his or her waking hours. This seems a daunting way to introduce meditation to a newcomer. Also, for many people, it could be difficult to arrange for 10 days without family or work obligations. Thus, I ask: What does the student gain by through an introduction to meditation via a "marathon" retreat?