Q&A sites offer that kind of info from experts or from everyday people. That's part of the appeal, too. It's kind of like asking your neighbor, coworker, or friend a question and getting a written answer.
There are some questions that cannot be answered by even the best reference books or encyclopedias. They need a human expert that can understand a complex relationship. or explain how to do something tricky. Some of those questions are difficult to ask face to face as they are embarrassing, or you just do not know anyone who can give you the appropriate advice. That is where Q&A sites excel. Bringing anonymous experts to people in need.