This is privacy with a vengeance. There are probably at least two reasons why teaching is such an intensely private activity. Likewise with service. Faculty members may read a tenure candidate's dossier in the privacy of their offices, but then they go to a meeting and talk about it. There is no such mechanism for teaching.
Teaching involves only the lone professor.
Teachers may share and discuss and form a community with their students, but not with their colleagues, their peers, their equals.