This is all part of the same problem. Yes, in the past, sometimes someone did post a thread-ending post. But, more often, a well-formed post didn't end the thread, but would lead to more questions and more discussion once the initial question was answered. I think this is the lack of intellectual curiosity Cyrus is talking about.
We used to get questions, even from students, that didn't have simple answers. They were people seeking more information than you could get out of a textbook or in their courses. The questions would require delving into the literature and piecing together information from multiple sources and sometimes coming to the conclusion that there really wasn't an answer to the question, but lots of indirect evidence that really opened up discussion.
Now, too often, the questions getting asked are so basic that all anyone needs to do is point someone toward a textbook (because students don't read books anymore).
Though, I'm trying to figure out if this is a problem with the direction of PF, or with the current generation of students in general. Just the other day, I actually had to show one of my students (halfway through the semester in sophomore year) that the textbook has an index and how to use it. And, I am wondering if we're NOT helping them to keep providing answers to simple questions rather than just telling them "go look it up in your book" so they learn these skills of using reference materials to find their own answers rather than having everything spoon fed to them. This is different from the way we help them work through homework problems, where we do make them do their own work, but more the simple questions that get posted in the regular forums that are still probably for their classes but not problem sets.