That's because someone has already taken pains and spent considerable time and effort to write those manuals and document any existing issues. Many times veterans also find themselves googling around in order to reply to a so called *new user* . And since he/she is a *new user* , its very likely that his/her problem is a very common one, and many such *new users* have already asked that question before.
Yup, I agree that most of these questions have probably been asked and answered before. The problem is not in referring them to documentation but rather the abrasive nature of the replies which make some forums an extremely hostile environment for new users. (I'm not claiming that this forum is, btw. I'm making a more general point.)
-Anshu