You are right that most stuff get's started in the beginner's section.
A lot of chit-chat evolves naturally from a post, trying to stop threads evolving that way and getting people to move the chit-chat elsewhere tends to stifle the it and it just stops and doesn't move elsewhere, which is why we prefer to just let it happen unless the original poster objects.
I'm not sure how we get people to post in more places than just the beginner section. It tends to be a a default place for people to post if they don't know where else to post. I mostly try and start my threads elsewhere now I'm no longer a beginner, but I'm not sure how we encourage more of this without becoming too dictatorial