I *think* it may well be a challenge that particularly appeals to writers who are interested in the craft of writing - at least, I can't find a better way of putting it than that. We all feel the desire to write down our own story, of course, but not everyone who writes wants a challenge that so particularly addresses the 'how do you write?' question.

Perhaps writers who like this craft challenge have a greater tendency to be writers who will produce sharp-edged work of their own..? Or perhaps, the sharp-edged ones are easier to remix? Hmm. It'd be hard to remix a comic story skilfully and keep it funny - though it can be done.

Note that the only two JuC stories I have written were done for challenges!