Perhaps one reason for this is that teaching is a private enterprise. Done behind closed doors teaching has been protected from open view under the cloak of academic freedom. Some of us have hidden poor teaching and many others have failed to be noticed for their excellent teaching because of a reluctance to tread on protected ground. Open observation of teaching that is voluntarily engaged in will take teaching out of the shadows both for scrutiny and for celebration. This would enable us to recognize and meaningfully reward faculty endeavors to improve teaching within and outside the classrooms, and to stimulate faculty members to evaluate their effectiveness as they participate in such mutual support.
Professors have little trouble quantifying their research endeavors.
Quantifying comes before qualifying. The Center for Teaching, Manhattan College, Riverdale, NY Br.