Here's the deal. Or rather, here are six of the deals.
1. It might be something you didn't think of.
I'm going to call out Why do I see this yellow color shift at high ISOs and fast shutter speeds? as an example of a great question in this regard. The answer turns out to be in a detail that the asker didn't think important, but diligently mentioned anyway. Because that detail was there, someone who knew that it was important could easily respond with an answer that we know is right, not just speculation.
2. If the answerer has to guess, so do the voters.
This is a collaborative community site, and while individuals have ownership of and responsibility for their own answers, the voting is what makes it work so well. If I come across a question and I know an answer is right, I can vote it up, and enough votes make it clear to the question asker and to future visitors that the answer has a high degree of confidence. (And it's also the "currency" of the site, giving the answer the credit they deserve for helping.)
3. It helps future visitors (in two ways!)
A. Someone else might have the same problem. By describing the issue clearly, you make it easier for other people to find in the future.
B. Someone might have a similar problem but actually significant difference in details. Then, the answers might not actually apply, but appear to to new visitors. This is making the internet worse rather than better.
4. Maybe the answer is already here.
That last point goes the other way, too. Maybe you are the "future visitor" and just don't know it. If you provide details, we can quickly tell if there is an earlier, already answered question which will help you right away.
5. Or maybe it isn't
Maybe the question appears superficially similar to existing ones, but there is actually an important difference. If you don't mention that difference, your question is very likely to be closed as a duplicate, leaving you without a good answer for your actual problem.
6. You want help, right?
And finally: while it's true that helping people with their question is the mission, remember that the people actually doing the helping are doing it for free, with no reward but ultimately valueless points and digital stickers. By making things nicer (and more friendly) for those trying to help, you'll get better help. Please read How do I ask a good question? for more.
Be as descriptive and clear as you can. Even if you are having trouble describing what the issue is, try. It doesn't hurt, doesn't really take that much more effort, and has significant benefits for you, for the other site members, and for future visitors.