Most people figured that with such a simple assignment (not significantly harder than the first one, which was also easy-ish) they could put off doing it until the last moment.
Most people failed.
This real world data needed hours upon hours of cleaning before it was in any way useable. Of course, the teacher knew this, gave bonus points to the ones who did start in time, and then extended the deadline as he had expected to from the start.
Never again will I underestimate the dirtiness of real world data. One of the best teachers I had.