I see these two policies as complementary, serving as brackets to eliminate two extreme sorts of questions we'd like to avoid. I suppose if the "brackets" were too wide there might not be any middle ground remaining, but I don't think that's a problem we're having.
On the one hand, we want questions that have answers. There are plenty of interesting questions that don't have good answers, and shooting the breeze about those sorts of questions can be a lot of fun. But that's not what the Stack Exchange is for. We have a little flexibility since we can use the chat server for those sorts of open-ended questions. But the model on the main site, with questions, answers, and (ephemeral) comments, is explicitly designed to discourage open-ended discussions. A predecessor to Stack Exchange refers to such questions as chatfilter.
On the other hand, we frequently have new users who will paste a multiple-choice homework problem into the question box and seem to be expecting someone to answer "it's (c)." Those sorts of questions don't have any value for anyone except the asker --- and don't really have much value for the asker, either, since context-free answers don't have any explanatory power. A good homework-like question isn't "what's the answer to this question?"; it's "how can I arrive at an understandable answer to this question?"
There's a pretty wide grey area at either end of these brackets. There are homework-like questions that some users see as interesting where others see low effort and low value,. Some users may see a question as open-ended or opinion-based, while another user may be able to provide factual answers.
That's why we have community moderation.
If you spend some time reading highly-scored questions and answers on subjects that interest you, I think you'll get a feeling for the broad range of questions that have interesting answers that become clear with minimal back-and-forth.