This question has been closed because it is considered "useless for future visitors".
Stack Overflow, the first of these sites, is highly successful since if you have a problem you can go there and post a question about it, and if the question is well written and you're lucky, somebody will answer to you.
Sometimes the question is a general one which might be useful for future visitors, often it isn't. There are PLENTY of problem-specific questions that aren't likely going to be useful to anyone else. Still, they are in-topic, and they receive proper answers.
This is how the first site has been build and has become successful. Now, if this site is going to alter this core policy I think it should have a very good reason to do so. I failed to come up with any reason that would apply to this site but not to SO.
Furthermore, this policy is, pardon my french, patently stupid. What's the point of "I'll help you if you have a reusable problem, I won't help you otherise"? It's just arbitrary. A Q&A site is good if you know you can go there when you have a problem, to receive answers. This site instead wants to focus on solving at whim only some problems and not others? Nonsense.
I have the feeling that this policy has been born out of ignorance on how the SE sites actually work, about which are really the policies of the main sites. I.e. both mods and part of the community "thought it was done this way", so they decreed it is. Wake up call: is isn't!