I get where you are coming from, the second is way larger because lack of motivation applies to everyone and there are only so many hours in the day with work, family, hobbies and entertainment all competing for time.
If a course is required as part of somebodies job it will get done.
If a course gives the person a list of letters after the name or looks good on the C.V. it might get done.
If a course is not required it is only going to get done if it presents a huge amount of value, like a new skill such as programming or learning a new app, it may get done.
Studying for the sake of it is a small group.
Curiosity can often be satiated with Youtube videos like Ted Talks or a podcast or maybe a book without needing to take any courses.
I am interested in car audio and I found by watching channels where people have done builds along with manufactures deep dives and tutorials along with my own experiments I have learned much about that subject and hobby. I would NOT be interested in taking a course it might RUIN my interest and feel like work.