The number of questions asked in a lesson is directly proportional to the quality of the instructor.
The frank truth is that most college professors have had no training in instructional design or delivery. They are ignorant about how to create an atmosphere of learning.
Learning is most likely to happen when there is a role for the student, in the lesson. Instructors should design their lessons to provide involvement, participation, and engagement for the students.
There is an old Confucian saying:
“Tell me, and I will forget. Show me, and I may remember. Involve me, and I will understand.”
In instructional design, we differentiate between the formal lecture and the informal lecture. The formal lecture is the scenario in which the instructor comes in, essentially reads a prepared speech without interruption and then opens the floor for questions. An informal lecture, although planned, is delivered in a more extemporaneous way, with allowance for diversion based on the needs of the students. While most instructors would say they follow the latter, they create an atmosphere where it is the former that dominates.
An instructor that says there isn’t time for questions should be tarred and feathered and clearly hasn’t been well trained. A good instructor knows how to use questions to propel a lesson forward.
The students are paying for the opportunity to ask questions.
That said, there certainly are instructors that do things correctly and create an interactive atmosphere in which the student feels like a participant and not an observer, and good discussion and learning happens.
Keep all of this in mind, and design your lessons to suit, and students will ask questions.