While the typical answer of "to prove your time investment to a third party" is a good one, I don't think that aspect would be relevant for me. For me the answ

While the typical answer of "to prove your time investment to a third party" is a good one, I don't think that aspect would be relevant for me. For me the answer would be so I know where I stand. e.g. I come back after a year or two and I know what material I have covered and what steps are next in the learning journey. I don't want to get three lectures or more in and realize I'm rehashing material, or, alternately, that I am hopelessly lost because I've skipped a pre-requisite and have to go digging for the missing piece.