All new members receive a welcome PM and email which includes a link to the
Novice's Guide To Using The Forums thread, but we still receive a few messages each week from new members who cannot work out how to post a thread.
All new members are required to agree to the forum rules during the sign-up process, with a very clear prominent link, yet it is clear that some don't read them.
The same is likely to apply with banners all over the place. As they say "you can lead a horse to water...".
We do try to steer people to existing threads and posts of relevance too, but as Dave noted this seems to go unnoticed. Some people are just looking for an easy "quick fix" solution, and as we know that often isn't possible.
All we can really do is have the information available and hope that at least some people are reading it. We don't know how much worse things would be if the information wasn't there, and don't intend to try and find out! Obviously as moderators we mainly deal with the minority of posts and members that cause problem, rather than the majority of problem-free posts and members.