Students can work together even though they are in different locations. Cost savings can be significant. Travel costs go away, as do child care costs. The learning environment is active, student centered, and leading edge. The comfort level goes up.
Students can work at their own pace, at their own best times.
There is time for reflection before responding to questions. Information is automatically stored in written form, and is archived. Students and teachers can have a permanent written record of all work and commentary computer-searchable for later review, study and update. And this is never more true than if the choice is between an on-line degree or no degree, which is often the case.