To protect you from spending time and effort on an answer that ends up being off-topic
If you answer an unclear question, there’s a risk the original poster or someone else may later edit the question in a way that makes your answer off topic. Preventing people from posting answers to closed or on-hold questions helps prevent this from happening.
To protect the original poster from being misled
If you answer an unclear question, the OP may think they got what they were looking for, while they actually still have a misunderstanding that nobody was able to address. This being the case, we’d like to encourage the original poster to clarify the question before an answer is posted.
Closing a question can send a signal to the OP that they have to communicate what they’re looking for more clearly, and keep paying attention to comments asking for clarification.
The /ɔ/ question: my overly-pessimistic, worst-case scenario
Here's the specific question that seems to be relevant. The problem I have with this question is that it’s not clear about what its purpose is, which I feel is vital for a list question. Since a complete answer is impossible (we can’t list all the words with /ɔ/), we need to know criteria for judging which answers are the most useful for the OP.
Obviously, any answer will have to deal with dialects, since this is something that varies dialectically. But we don’t actually know that the main question is about dialectology. That is only one interpretation of the question. It might actually be about phonetics. The question uses phonemic slashes, true; but it refers to the "/ɔ/ vowel sound" as well as using the symbol "/o/," which is ambiguous in the context of dialectology, and referring to "open back" counterparts of this vowel.
Here’s a possible “worst-case scenario” where the questioner doesn’t actually care about dialectology: imagine a person is learning Italian, which has contrastive /o/ and /ɔ/, and wants to learn how to pronounce /ɔ/. This person decides to look for example words in English with [ɔ] to help them learn the vowel sound. They assume that Italian /ɔ/ is phonetically [ɔ], and English /ɔ/ is phonetically [ɔ] (an easy assumption to make, but not necessarily a safe assumption). So, they make a post asking for words with the /ɔ/ sound in English.
Someone responds with a list of a few sample words with the /ɔ/ phoneme, a description of lexical sets, and discussion of how members of this lexical set vary across different American dialects. This would be a great answer to a question about the dialectical phonology of /ɔ/. However, the original poster misses out on learning useful information about the phonetic details that were actually the original motivation for their question.
An important point about this imaginary scenario is that nobody – the original poster, the answerers, and so on – will be able to realize that the original poster was motivated by an “unsafe assumption,” and missed out on useful information. The original poster thinks that they’ve gotten the information they need, and the answerer thinks they’ve provided all the relevant information about /ɔ/ in English.
Is this story far-fetched? Yes. But I don’t think you can disprove this story about the OP of that question, because they have not responded to anyone or clarified what their question is really about. Until that happens, or until someone decides that the OP has abandoned the question and edits it to have a clear purpose, there aren’t any objective criteria for selecting one answer as the best for that question.
An idea for what to do
If you really want to answer a question that was suggested to you by someone else's question, I think the best solution would be to post it as a new question. I assume it would not be closed as an exact duplicate if the original is closed for being unclear. For example, in this case, you could post and answer a question "Are there differences in the distribution of the phoneme /ɔ/ across different dialects of English? If so, what are they, and what are the relevant sound-changes and cross-dialectical correspondences?" I think that's sufficiently different from "give me words with /ɔ/" that it wouldn't be closed.
I'm unsure about this suggestion, however. Perhaps it would be better to simply edit the OP's question to what you want to answer, and then see if the OP responds.