[O]nly (good and great) portraiture requires the photographer to enter into a relationship, a rapport and a collaboration with the subject. No one walks in cold and, on meeting a portrait subject for the first time, fires off five or six frames, deludes themself that they have a perfect shot, and terminates the session. Unless your only goal it a clinical documentation of the person in front of the camera.
In other words, you have to develop a connection and get to know another human being. That isn’t easy.