If a section is removed, posts that would have gone there will be posted elsewhere where they are even less relevant and more disruptive to that particular section's goals.
On the other hand, providing a section for those sorts of posts will encourage them, making them more common, at the same time as keeping most of them out of the way of the rest of the forum.
For example, if the forum games sections were removed, then DF-related games would become plentiful in DF general discussion, potentially drowning out the other ctopics, and the rest would tend to fall in community projects and Finally...'s general discussion. Removing the section will not just make all of them disappear.
Consider this: One section was split because half of the front page topics were different (I think it was either forum games splitting off from VN, or RTDs splitting off from forum games, or perhaps both), but in both cases it greatly reduced the clutter at the time.
Actually, I think it was FG&R (or perhaps all of the new sections?) splitting out of VN, leading to greater concentrations of nonsense that lead to the downward spiral that got that place locked. However, once VN was locked and hidden, it has been slowly creeping back in, mainly into GD. This is obviously not a good thing.
Perhaps it could be solved by splittig GD into GD and a sub-section of GD intended specifically for the less serious discussion, but it could also be solved by peroperly educating the offending users on why their comments are disruptive to the threads they are posting in, and how they should keep such comments to more appropriate locations, like more suitable topics, or for the worse ones, other forums entirely.
Finally, making it public knowledge of when/why a user is banned would allow others to learn from their mistakes, and hopefully teach them to think about what they are posting more often.