Any subject can be made interesting, and therefore any subject can be made boring. -- Hilaire BellocWhy do teachers at all levels lecture so much? First of all, lecture is a cheap "delivery method." Class size can be maximized once lecturer-student interaction is dispensed with. Lecture is not, however, an effective means of developing and tracking knowledge or skills in a great many people.
Second, lecture is the easiest technique for the teacher to develop a modicum of skill at. It requires minimal preparation. (A fast talker can "wing it" from time to time apparently undetected by his audience.)
Third, and not the least important, the emphasis on lecture obscures the common perception that pedagogical skill is inversely related to level taught; that is, elementary and middle school teachers tend to be better at pedagogy than high school teachers and college professors. (Many universities go through an elaborate ritual of denial by bestowing MacArthur awards for teaching on – usually, assistant -- professors whom they later reject for tenure.)
To examine these issues further, see “ ‘The Mind's Eye’ and Pedagogical Practice”