Actually why is it needed in the first place? There another setting for course subscription in the course details (auto, on-approval, etc), so what is the purpose of this checkbox? I see also it's inactive in classroom courses, meaning that it's only used with elearning courses, but it doesn't save status. I think this is the reason why the admin doesn't get notification when users subscribe to courses.
even if you don't see why it's needed, it doesn't mean it is useless. The purpose of the checkbox is to save a lot of time. If it wasn't there, you would have to:
- create a course
- go to the subscription area
- enrol yourself and then change your level to administrator or teacher.
The checkbox lets you do all of the above upon creating the course, saving you a lot of time.
It's not true that if unchecked it doesn't save the status: if unchecked, the course is created and nobody is enrolled.
Finally: the box is inactive in classroom courses because classroom can only be created by first creating a master course and then the editions, it doesn't have to do with notifications.