Why is it harder to find an online CS degree program (graduate/undergraduate) than an online degree program in something like graphic design, nursing, criminal justice, etc.?
One guess is that the online-education route in CS more often just bypasses degrees entirely. If you're not going to go to a meatspace university and attend classes, the online-only alternative in computing is usually to learn a bunch on your own, start participating in projects and building up a portfolio, and then try to get hired on the strength of that.
I suspect it has to do with the type of student that generally looks for online programs and what they're looking for, flexible vocational training. It's not just CS that's rare online - try to find any science program, for example. Science degrees train researchers and scientists, and these people aren't the type that need an online degree.