It’s always the same question that comes up, when I’m reading and watching coaches teaching tennis. These colleagues, willing to do the best for their players, are using methods, that are absolut contradictionary to evidence based coaching.
They focus on body motion, they try to provide text-book techniques, they let players stand in a row to control the technique, and so on.
I think, there are two main problems: 1. a lot of coaches do what they „have always done“. They transport methods, they have learned in their own tennis biography. 2. coaches are tennis-coaches. Means they seldom look over the „plate’s edge“, where tehy could find so many studies about motor learning and creativity in related sports as golf, volleyball, basketball, soccer and so on.