The K-12 system covers all the subject for classes from Kindergarten to Grade 12. Creating courses for all the classes is next to impossible for a single person. For example, take the curriculum for a Fifth Grader. There have to be separate courses for the mandatory subjects like English, History, Mathematics, Science, and Geography, each of which has 10 chapters at the very least. Apart from these, other activities like P.E., Drama/Poetry, field trips and the like, also need to be accounted for.
The administrator cannot get bogged down by creating all of these courses himself. However, neither can he make all of the teachers ‘Administrators’; it would completely break down the hierarchy of the website. LearnDash sidesteps the imminent chaos by incorporating the ‘Instructor Role’ add-on which lets the Administrator add teachers as ‘Instructors’ instead of ‘Administrators’. The way this works, the teachers are free to design and conduct their courses, according to their respective subjects, without interfering in the administrative section of the core website.