Teacher to student lecturing happens for a combination of three reasons:

1. The teacher believes it's the best way to present the material.

2. Generally, a lecture is easier to prepare (and easier to keep on task) than any other form of instruction.

3. To the average person (and many administrators) a classroom full of children sitting silently in rows, all taking notes, looks "right".

In a good class there is no distinction between learning from the teacher and the teacher's assigned material because each is required to excel in critically debating and responding to the other.