A game like TES has so many aspects and facets - not just "talk" and "kill things" - that one thread cannot possibly organize diverse suggestions into any useful format.
When people start to start a general discussion about a certain topic we usually allow it - but the key phrase there is "general discussion." So a thread discussing where people want to see the next game set is generally fine while a thread saying that the next game should be set in Hammerfell and here's why will usually be directed to the suggestion thread - or better yet, directed to an active thread discussing game locations since that's a great place to post why you think Hammerfell would be a great choice.
Threads discussing a topic are usually far more productive than a thread discussing one person's idea about one thing - or even worse one person's ideas about a dozen unrelated things. Allowing the latter would also result in dozens of disparate topics, many of them repetitive and most of them lacking any real discussion. In fact it would probably have all of the problems of the current thread but spread across far more room.
This isn't to say we need an official thread for a dozen general topics concerning TES V, while better it's still congestive. However if there are a few general threads, particularly if they're cast as a general "what would you like to see" rather than "what would you like to see
in TES V I think this forum can maintain that discussion you're looking for without causing problems. In fact I'd say this forum already manages to accomplish just this quite often.
Well it's not completely useless, I mean, moderators have said in the past that the devs read it at least occasionally. Though, with Bethesda likely far into development of TES V by now, they probably don't look at it anymore. It seems it would have been pretty useful after Oblivion was released.
That was true when the thread first started but I don't know how long the devs checked it out.
That isn't to say the devs aren't looking for people's opinions about their games, they just looking elsewhere