I think the issue is one of scope. Some people want this forum to be a place to get quick quality answers for the worlds they are building for professional use, or similarly serious use. Others see this place to build smaller, less important worlds. Consider, there is no objective metric differentiating "Christmas in Space" from "Aquatic Intelligence," other than that it is very clear that the author of "Aquatic Intelligence" intends to incorporate it into a larger work, and it is less clear if "Christmas in Space" will be incorporated (but we don't know for sure!). Both are positively addressing a world that does not exist, and is being built (at minimum, being built on SE, as we speak!).
If one is of the mindset that the purpose of this forum is to support professional work, and nothing more, then these smaller questions could be seen as crowding out. The other mindset would suggest that these other questions attract more attention to the forum, giving the professional question askers an even larger audience.
The line between acceptable or not has to be fuzzy. As an example, I posted a puzzle question a while back, and the community decided this forum was not the place for puzzles. However, the question itself was valid (so much so, that I received several suggested edits to try to bring it around and get the hold released). The presentation mattered so much, that the actual content was never called into question, even though I openly borrowed content from popular questions of the time. Other than my choice to present the quesiton as a puzzler, there was no way to discriminate between it and the serious Faerie and Magic questions around it.
I would err on the side of caution, and allow more "funny questions" over closing them. Give people the benefit of the doubt, or we run the risk of starving the forum as people fear the moderators closing all of their questions. If we need it, a tag might surface to denote "serious work" for those who would like a smaller, more dedicated audience to answer it. Jokingly, may I suggest "Serious Inquiries Only" as the tag name? ;)