Hoda,
I hope art therapists who are leaving the field are taking their training with them and applying it to the work they do, because they would then still be connected to the heart of art therapy. It's not leaving or not leaving the field that matters, it's how people leave it, and they will, at least until the field catches up with them, because the exploration of new territory is a normal part of the expansion of a healthy growing field. New art therapy graduates should not feel defeated if they accept work in novel and (God forbid!) creative positions.