You need demonstrations to help the student visualise what you are talking about. Imagine an ab-initio student attempting to land for the first without ever seeing it done before.
Sure, but only once, then let the student try a few times, if he or she has obviously not got it, demonstrate again and then let the student do it a few more times until they have got it.
The only way to learn complex motor skills, and the judgement that goes with them, is by actually performing the task, not watching someone else do it. Most of what an instructor does when demonstrating a manouever is completely lost on a student as they cannot feel his or her inputs - they are simply observing the expected visual cues.
And even if all that wasn't true, the student is paying money to fly, not to watch an instructor fly.
This yet another reason why sensible CFIs try to find a few older, experienced heads for their team. The older ones generally get it.