The goal of the site is to help you build your world, not to tell your story — Help Center
"Why would X?" questions are considered on-topic,1 but are also notoriously too broad, primarily opinion-based and/or too story-based. So, the rules for asking one are (IMO) as follows:
You MUST be asking about your world, not your story.
- Worldbuilding is about systems, rules, and their consistent application.
- Storybuilding is about circumstances, actions, and plot.
- "Why" is inherently seeking a justification or rationalization for something, and 99.9% of the time that something is a circumstance, action, or condition of the story's plot. This is perhaps the biggest reason why "Why would X?" questions are so difficult to ask. They're almost always asking for help overcoming writer's block (off-topic), not help building the rules and systems of a world (on-topic).
You MUST provide a LOT of limitations, conditions, and (most especially) expectations.2
Consider the following question: "Why would a fish swim upside down?" I can think of several answers: (a) it's dead, (b) it's been poisoned but isn't dead yet, (c) It was just hit on the head by a fisherman, who then lost his grip, (d) the sun feels good on its tummy, (e) it's been bewitched by Elizabeth Montgomery... Unless you're trying to overcome writer's block ("I'm stuck! Just throw some ideas at me!"), most of those questions are obviously inappropriate — but because I did not provide an expected outcome, the respondents did not know that and threw everything under the sun at me.
"Why would X?" questions are always fishing-for-ideas questions. We are very restrictive about these kinds of questions because they break Stack Exchanges expectations for how their sites are used in a lot of ways.
- Unbounded or poorly bounded questions are asking for an infinite list of things, which is off-topic.
- Identifying boundaries by listing conditions, limitations, restrictions, and most importantly, expectations, goals, and results make the question a finite list of things, which is on-topic.
- Asking for help with cultural worldbuilding could be a common "why would X?" question, but you must be focusing on an organization (not people, there's a difference). Frankly, cultural worldbuilding is very similar to developing a magic system. You're creating rules and systems and investigating consequences (consistency of application) to stimulus. Cultural worldbuilding questions (why would X?) must be asked in basically the same context. Remember, you may be trying to write your story, but we don't do that here. You need to ask in the context of developing a rule or system.
I would be delighted for more people to contribute to the cultural worldbuilding meta question as it touches on this issue particularly. When you ask "why would X?" the question cannot be of a form that is legitimately answered, "because you, the author, want it to." That means including reasons why "I, the author, can't simply want it to" along with expectations and goals so a best answer can be judged.
Stack Exchange's fundamental design is to help people solve single, specific problems.
SE is not a discussion forum. Unbounded "why would X?" questions are inviting discussions.
Our Help Center explains that questions must be specific and answerable, must include context, must include restrictions/requirements, and should include research. Most "why would X?" questions only provide context (and then wonder why they're closed).
- These questions cannot be high concept questions.
- These questions cannot be open-ended questions.
Just to reiterate: unbounded idea-fishing is off-topic. Frankly, if a user can't reword the question to avoid being a "why would X?" question, then I would recommend always posting it to the Sandbox first. It's easier to deal with there and it won't cause Stack Exchange's automatic user analysis to ding the user for a closed or downvoted question.
Finally, it would be unfair to not note the basic caprice of this site. When a question tickles people's fancy, they answer it whether or not the question is appropriate for the site. If they don't like it, they downvote and/or close even when the question meets all the site rules. This site enjoys a much higher level of caprice than any other SE site on which I participate. I've slapped (and continue slapping) a lot of hands, but in the end, it is what it is.
1 This might deserve reconsideration, considering how much trouble we're having with this type of question.
2 The Help Center uses the word "requirements." I prefer the words "expectations" and "goals." They all mean the same thing. You can (a) tell us the situation and ask for help with the outcome/expectation/goal/requirement or (b) tell us the expected outcome... and we'll help with the situation, but you cannot ask for both. "Why would X?" questions should be providing the outcome/expectation/goal/requirement as it's obviously asking for help with the situation, but far too often they ask for both.