Probably because he/she has tons of videos that walk through setting it up on c9.io's old site.
I'm also a course creator (but I don't use cloud9). A change like this is a really big deal for someone in his/her shoes. Having to re-record all of those videos is non-trivial, and doing it with the self hosted version would still require new videos to be made.
I'm not saying it isn't a hassle. But that is a better solution then rerecording everything. If you come up with a self hosted solution for c9, I would hope that the courses have a single video for setting up cloud9 which would be better then rerecording everything.
I feel for them, but it is the risk associated with using any sort of product you don't directly manage yourself.
I'm also a course creator (but I don't use cloud9). A change like this is a really big deal for someone in his/her shoes. Having to re-record all of those videos is non-trivial, and doing it with the self hosted version would still require new videos to be made.