The more students taught, the more students are affected by these bad habits. By the time these students realize they are not following the Principles, they may have to change years of training. Just as easily, Instructors could teach the Basic Principles, and save these students a great deal of wasted time and effort. As their Instructor, you think they look pretty good because they look like you. It satisfies your ego, but it may have nothing to do with the Basic Principles.
Training has the ability to be medicine or poison.
Following the Basic Principles is medicine for the body and mind. Without following the Basic Principles, training can be poison. Over long periods this poison manifests itself as muscle and joint damage, cancer, or heart disease. Without following the Basic Principles, and balancing the spiritual and physical aspects of training, serious misunderstandings are developed by the student. Over time these evolve into improper beliefs and behaviors.