It's so very common to see people compare playing RPGs solo to "novel writing." Yet, they don't seem to be aware that all that separates social roleplaying from collaborative novel writing is the medium. Move their medium from speech to writing, and there you have it: collaborative writing.
What I think people can't articulate when they take their pot shots at solo roleplaying is that they think that the back and forth feedback between people is essential to RPGs. But then again, if the back and forth feedback was in the written form, what separates their activity from collaborative writing?
Nothing that's what.