Most of the questions receive good answers. A few questions tend to be quite specific, though--asking about one specific property, often in some out-of-the-way location. In that case, it takes an agent who works that area to see the question and respond to it.
Sometimes the questions go beyond an agent's scope of practice--asking detailed legal questions, for example. In those cases, it's likely the responses will be along the lines of "Contact an attorney."
Sometimes, with questions sort of like yours, the reaction is, "Huh? That's not my observation or opinion" and--rather than specifically disagreeing--agents will just move on to questions they feel they can best answer.
Similarly--and again, like your question--the "set up" doesn't match the question. You say you see questions but "there's never really any answers." OK, that's an observation. But then you ask a totally unrelated question about whether someone manages this website. One is unrelated to the other. And lots of agents just don't understand what your point is.
Sometimes agents prefer to answer specific real estate questions, rather than "just curious" questions that really aren't about real estate. Such as: "How often is this site updated?" Or "Where did you get the information for my property from?" Those questions are best answered by Trulia support.
Sometimes a person will post the same question two or three times. Usually, the pros here will start with one of the questions and answer/respond to that...rather than spreading their answers out across three identical questions. If you happen to look at one of those duplicate questions, you won't see any answers because all the answers are on one of the other threads.
Some agents use Trulia almost exclusively as a marketing tool, so if a question doesn't provide an opportunity for them to offer their services, they tend not to answer. Nothing wrong with that; it's actually an efficient use of time. Others--the ones you see posting a lot, usually--also see Trulia as a way to help consumers with real estate questions.
Hope that helps.