Yet all the mer shared the same voice and the Orcs and Nords shared the same voice in Oblivion. If diversity is a good thing, why'd they do that? To put it simply: The sharing of voices was to save disc space. Why do you think they had awesome Dunmer voices in the infamous e3 trailer, which we never saw?
The whole "living away from Vvardenfell" excuse is lazy, poor writing that should never have even been necessary.
Just because a race lives away from thier homeland, that gives no reason to sap them of all thier culture and uniqueness. You never see a non-scottish nord, do you? I mena, they where all over Morrowind and Oblivion.
Okay, first of all, I thought the Dunmer voices in the e3 trailer were annoying as hell. I would have hated listening to all of the dialogue from the Dunmer in that voice. It worked in Morrowind because there was less voiced dialogue in the game, but going through Oblivion listening to every conversation between NPCS, and every conversation with the player, in that tone of voice, I think I would have gone mad. It's bad enough listening to Ghouls in Fallout 3.
My argument isn't that when Dunmer move away from Vvardenfell, they magically get their voices healed. What I'm saying is that Dunmer who were born in the other provinces, who have most likely never been to that weird, xenophobic little island for more than a few days at a time, would not have the same exposure to the air and hence, their voices would be different.
But your argument about accents doesn't make any sense. When people move away from their homelands, they retain whatever accent they grew up having. But their children who were born in the new land tend to speak like the natives of their new home (for example, Asian-Americans and their children). It may "sap them of all their culture and uniqueness." What we got in Oblivion could easily be the Merish equivalent of a Cyrodiilic accent (with their different biology accounting for why they don't sound exactly the same). As for why the human races still sound unique, I don't know what to tell you, except that the fan uproar would have been even greater if they had had Nords that sounded like Imperials.
You've rehashed your disc space argument in I think every thread that voice acting has ever come up in. I GET IT. My point is, that it worked out for the better in my opinion because I think the voices we ended up with are more lore-friendly. I'd like every race to have its own voice, obviously, but I would prefer if they stayed in the vein of Oblivion.