The suggestions thread is a dumping ground to keep people from making hundreds of pointless threads. Game developers are in a position to turn their own ideas into products, they don't need a bunch of forumites to tell them what to do.
Game developers with a userbase as large as Bethesda's aren't in a position to turn their own ideas into products within their most important and successful established franchise, no. With a new franchise? Maybe. But when a series is as big and as important to a developer's success as this one is, they can't afford to just do as they please. The business simply doesn't work that way.
And Bethesda in particular doesn't work that way. Their focus seems to be on two things: trying to broaden the audience for their products as much as possible without alienating their core fanbase, and trying to correct the issues people see in their games. The issues they're trying to fix are specifically from feedback they've received from their customers, and that feedback includes these forums. The intent on broadening their audience, to a fair degree, informs the approach they take in trying to fix said issues. All of this is pretty apparent in Oblivion: Morrowind's combat system, the difficulty of the game (either for being too easy or too hard, often because players would get in over their heads early on or would play it far too safe until everything was a bit of a joke for them), certain quests involving exceptional difficulty in finding things, the overall quest design, excessive amounts of forced wandering during many of the quests, the horrendously bad (read: almost nonexistent) stealth system, the gray-and-brown look of the game, the lifeless dialog and poor persuasion system, statue-like NPCs, downright silly lockpicking... these were all major points of criticism for the game, and things that came up the most among people who enjoyed Morrowind. So Bethesda's response involved completely overhauling the combat, introducing level scaling to try and control the game's difficulty on a bit of a broader scale, introducing a compass that more or less constantly tells the player exactly where to go, focusing on fewer quests with far more complex game design involved in them, introducing a fast travel system that could get you where you were going near-instantly at almost any point in time, introducing a full light-based stealth system, bringing it to a fairly typical fantasy setting filled with bright and vivid colors, voicing every character and introducing a minigame to make persuasion more involving, using an AI scheduling system to make NPCs actually move about and do things, and introducing another minigame to handle lockpicking (again, in an attempt to make it more involving). You can see them doing similar things with Fallout 3 - things like the minigames were made a little more interesting and believable and a little less impactful and exploitable because they were a major issue people had with Oblivion, they introduced nav meshes because of complaints to do with Oblivion's pathfinding, and they scaled back things like the fast travel, the quest compass, and the level scaling pretty significantly. I could even pull further back and go into detail about how Morrowind handled criticisms of Daggerfall in a similar way, but... well, this post is long enough.
Do Bethesda take significant game ideas from their forums? No. Absolutely not. But they absolutely do monitor the input they receive on their games, both here and elsewhere, and from what I can tell that seems to be the primary driving factor in a very, very large number of their decisions (and maybe even in most of them). If a large enough amount of people complain about the omission of a feature then they will often introduce that feature, and if a large enough amount of people complain about something about their games not being up to snuff then they will almost always tweak and modify that something in an attempt to fix it. This is one of the very few reasons I still bother to follow the company and buy their games.