I think people are seeing the site name of Programmers*, and assuming it's a Q&A site where they can ask programmers their questions, and get answers from programmers.
In actuality, the site is a Q&A site about conceptual software development, and it follows the same guidelines that most SE sites have about what makes a good question.
As Bill pointed out, the programmers faq makes it fairly clear what is and isn't on topic for the site, however many users don't think to read the faq before posting a question
The majority of closed questions are either
Code questions - These should be asked on SO. If the question quality is suitable for SO, they get migrated there instead of closed, although if not they simply get closed.
Requests for broad recommendations, like book suggestions, what to learn next, or general advice in X situation. Any kind of broad question like this is usually closed on SE sites as unanswerable since there is no one right answer to the question, and they usually turn into a poll with everyone chiming in with their own recommendation or opinion
- Questions about or for programmers, that are unrelated to conceptual software development. The site is meant for Q&A on conceptual software development, so questions asked should be related to that.
* The site is called
Programmers because it was originally going to be a site for Not-Programming-Related questions that programmers have for each other, however the site scope got changed quite a while ago. You can view the full history here