Well, some of the courses will have large overlaps. You might have 5 different courses teaching "intro to python".

Also, if a study group successfully finished an intro course, they might want to take an advanced course together. Or do some non-MOOC advanced learning.

After all, people aren't taking courses in a vacuum. They're taking them as part of a learning path. That path can include additional courses, exercises, projects, and a lot more.