Pilots love procedures. And for good reason. They help keep us safe and in good standing with regulators. They are good for airplanes, and they are good for flight schools as well. Every time an instructor goes flying with a student they use dozens of procedures, but often the student has absolutely no idea why.
Education relies on a series of building blocks, each one adding more information and context to the next. So it makes sense that in the beginning of training, we stick to the basics, only telling the student what the person needs to know to function. As the training progresses, it's important to push beyond that basic level of information to help the student start to form connections so he can think for himself. This is especially true with procedures ranging from flying technique to rental contracts.
Let's look at two simple examples.
In the first situation the student is about to take the runway and she flips on the landing light, as the checklist specifies. The instructor instinctively asks her to turn it off with no other instructions or explanation. That student has no idea that the CFI was in a meeting last week with the school's owner, who asked the staff not to use landing lights because they were costing too much to replace. This is a common practice at many flight schools, and because of this instruction the student will now likely fly for years without a landing light until someone else points it out to her one day. In other words, she won't understand why she was asked to do something, and will therefore have no reason to consider an alternative action any time in the future.
Consider a similar scenario with a flight maneuver. Here the student isn't very good at studying, and instead relies on the instructor to teach ground school and in the air. They are practicing power-off stalls, and the instructor's demonstration only includes an instruction to start a descent prior to leveling off to make the airplane stall. Without using the phrase "approach to landing stall" or discussing why they are practicing the maneuver, the student will never correlate the maneuver to an approach and landing environment, and half the reason to practice it in the first place will be moot.
These two examples are pretty common scenarios, and a few out of the many things a student will experience in a flight school. We shouldn't forget that the aviation world is foreign to students, and anything we can do to better help them navigate it will help increase their chances of flying safely.
So while it's fine on the first preflight inspection to ignore describing all the various imperfections we should be looking for, over time those vital pieces of context will improve learning and engagement in the flight training process.