Small classes are nice, but there is such a thing as too small.
When classes become too small, administrators raise questions about the efficient use of faculty resources. Prudent teachers, looking over their shoulders at the brooding presence of the dean, will strive to keep enrollments up, lest their deans tell them to offer a more popular course. Teachers frequently wonder how they can market these courses to increase enrollment. Some factors affecting course popularity are beyond the instructor's control. For example, some subjects are simply not engaging to some students.