Gigantism's appeal 1: something different
I'm going to start with the simplest explanation and move on to other reasons as I continue this series of posts. There's nothing intellectually deep about this one, but the simple fact that a setting where the characters live inside/within something vast is different from the more common medieval and classical settings found so often in fantasy...that appeals to me. Different isn't automatically a sign of greater literary merit or anything of the sort, but for me, being different is something I value in stories.
I'm a member of a few writing communities, and frequently the question comes up of whether an idea is over-used or something along those lines. The answer that generally comes back is that clichés become clichés because people respond to them, and that it's all in the execution. Good and useful answers for the most part...but at the same time there's a part of me that wants to say, "Yeah, but don't you want to branch out, discover something new, attempt something different?"
So even if it's not a reliable marker for a better story or greater merit, when I find something that has a different feel from things I've read before (not just in setting, though setting is what I'm talking about now), that's likely to catch my attention and make me want to read it.