Courses vs. Books for studies
There are fictional books we read for leisure, and there are highly technical books that can be treated like courses in a way. Maybe it makes more sense to actually organize and approach them as such?
There is also a problem, when the source is digital and cannot be touched or perceived in a 3D space (Related: Digital vs. analog books). Which makes it more difficult to come back to it. So we need constant reminders in our 3d world, like sticky notes. For example, if I am reading the SRE book, I need to keep a sticky note near my computer with the URL and title of the book to remind myself. With analog books you have the actual thing close to you that constantly reminds you that you are reading something. The same can be said about any digital project or course.