'Would' marks an imagined situation, not a real one. 'Why would the store close early?' asks what could make that happen, so it invites speculation rather than a stated fact.
The same question works both ways: Why would she lie? can mean what reason could there be?, or surprise, as in why would she do that?
One limitation: 'would' sometimes just softens tone, so a 'why would' question may read as gentle rather than hypothetical.
The same question, worked through
Take one question and follow it through: Why would the train be cancelled? The word would signals that the speaker is exploring an imagined possibility, not reporting a fact, so the question reaches into an imagined world rather than this one.
Because the situation is imagined, the question invites reasons instead of facts. A natural answer is because of flooding, or maybe a signal failure. The asker does not know what happened, so would keeps the exchange on hypothetical ground, like a thought experiment rather than an accusation.
Now suppose the speaker watches the train pull away without stopping. Their question shifts: Why would they skip our station? Here the imagined action has just become real before their eyes, and the same word now carries surprise or mild disbelief.
The same case also shows the softened use. A commuter asking a staff member, Why would my ticket not work on this train? may simply be phrasing a real problem gently. Would lowers the temperature, so the question sounds curious rather than angry.
So one word does several jobs in this single scenario: speculation in the first case, surprise in the second, politeness in the third. What unites them is that imagined distance, and the context decides which reading a listener hears.
The limit is simple: would holds an imagined event at a distance, but the word alone cannot tell a listener what kind of distance. Tone, context and even voice decide the reading, so the signal is flexible rather than precise.
Part of the edge comes from the pattern, not from questions alone. Would does many other jobs in English, from past habits to polite requests, so a learner who spots would in a question cannot assume speculation or surprise every time.
Because of this fuzziness, linguists still debate how would conditionals relate to their plain-tense counterparts. Some prefer the label subjunctive conditional, because counterfactuals are not always counter to fact. That debate is a good reminder that would works as a flexible signal of imagined or softened reasoning, so its exact force depends on the sentence and situation rather than on one fixed meaning.
Honesty closes the explanation with a limitation. Where the mechanism is clear, one word keeps the question on hypothetical ground; where it is not clear, the reading stays open, because 'would' alone holds an imagined event at a distance without saying what kind of distance, so tone and context decide whether the question reads as speculation, surprise or softened inquiry.