I agree - that's like writing a genre you don't like - or, for a fanficcer, a fandom you don't like. Not that writers don't get asked for that, and I've heard the argument used in other areas of life, too. Someone who wants you to do something you don't want to do is apt to say "Don't be so cowardly; step out of your comfort zone." It's a pretty effective argument (who wants to be a chicken who never tries anything new?) until you realize the motivation behind it is just to get you to do something you don't want to do, that someone else does want you to do for their own selfish reasons.:-) (You can easily see men using this argument to get a woman to do something sexual that he likes and she doesn't!)

So you shrug and say "It has nothing to do with fear, or comfort. I'm not interested."

I think that question, and the previous, are phrased poorly. The assumption that a pairing I don't write is one I (a) don't accept or (b) find uncomfortable is silly, and I don't suppose they really mean the question to sound like that. There's what you're interested in and what you aren't - and, as a writer, I've definitely found that at times I'm very interested in writing outside my comfort zone. Sometimes it works, sometimes it doesn't, but it's a good stretch when you're so inclined.