The voice teacher's ear is the most important tool that they posses. It is the necessary key to a practical application on any understanding of the voice, teaching method, or philosophy. The teacher must be able to hear what the student is doing and hear if the desired change was made, without this, knowledge of the voice is difficult or impossible to use in the studio.
I believe this is one reason that teachers dislike "voice science," because they find it difficult to apply. This is in part because voice science is often taught as concepts, equations, graphs, images and diagrams. While this information is valuable, it is not applicable until the sound of the voice is dealt with directly and deliberately. When an intimate understanding of the sound of the voice in relation to the principles of voice science is gained, the voice teacher will have a solid foundation on which to build and develop their techniques of instruction that are grounded in science and real-world applications.