The reason is that the employment target of pedagogy is mainly schools, whether it is primary and secondary schools or colleges and universities, all institutions, all of which eat national meals, which is "iron rice bowl" in popular terms.
If you are an interdisciplinary candidate and get a postgraduate degree in education, there is no doubt that you are the most qualified. Because as long as you have a basic subject, such as mathematics, physics, chemistry, biology, Chinese, English and so on. Now if you graduate, it is difficult to get into a good primary and secondary school, but once you graduate from education, you can get into a good school after graduation.
If you don't want to be a front-line teacher, it doesn't matter. You can go to a good middle school or research institute to do scientific research, or you can join a college and become a teaching assistant like a counselor. Because major universities are still recruiting a large number of graduate students to enter teaching assistant positions, and these positions are the first choice for education graduate students.