It isn't a fact, unless you can prove that it is the reason. The most vocal aren't always the most right, I would rather have it that people state there own preference rather than someone elses. It is well known that this particular section of the forum is biased against anything related to OB, so I find the poll results to be a good thing, because it means people thought for themselves instead of going with what is popular.
You know, nothing ever is without cause, so when you see a lot of people bash a subject, then there should be a reason for that.
As I have said in
http://www.gamesas.com/index.php?/topic/1146006-radiant-ai-in-oblivion-and-tesv/page__view__findpost__p__16765964, when making Oblivion, BGS has bitten more than they could chew, and had to throw out a large portion of that bite to be able to chew the rest, and fully voice acted dialog was a particularly heavy part of that bite, which resulted in a lot of under-developed game systems and content.
When you are manually placing a voice over on a line of text, you are limiting that line for a specific NPC, and you can not switch that NPC for another one, on the fly.
So you are putting a big handicap over dynamic AI and dynamically adjusted quests that could use any available and suitable NPC for a specific role, or quests that could switch an NPC in a role with another NPC, if needed, and so on...
You know, if we break out of the "Fully voice acted dialogs" shackles, we can move forward to a lot of revolutionary ideas for dynamically generated dialogs, better AI, and self dynamic repairing quests that would fix problem caused by missing NPCs, items and the like.
You can also read a lot of debate oscillated repeatedly in this thread, without being prejudiced, if you could, and see if those pre-voiced dialogs could not make a problem for the developers, and cause loss of depth for the resulting game?