At the university from which I got my BS, none of the other physics majors were preparing for teaching, as far as I can remember.

In mathematics (my second major), which had more majors in the department than physics had in theirs, there were a few who were preparing for secondary education. However, the math department had a long running special program to promote that path.

Pre-collegiate teaching us just not an attractive career to enter for most people who are interested in the more academic fields.