Dropping out has come to mean you will never get a degree because most people only consider college in the first place because they perceive a workplace advantage to having a degree. When they get out into the real world and realize they can live comfortably without one, there is little reason to go back. Someone who loves learning and is in college for reasons not related to future employment is not likely to leave over an idea in the first place.

Because of that, the number of people who leave and then go back is significantly small. Though I think you make good points anyway.