http://forums.obsidian.net/topic/78825-the-reason-why-a-lot-of-va-isnt-voiced/?p=1680668
After I made the post linked above, and observed the conversation that ensued for a while, I started thinking... VO is quite expensive. Like... really expensive. And if we assume that a game development studio has a given amount of money allocated to a game, say X dollars... then it follows that any money spent on VO is by necessity money that can't be spent elsewhere. That's how money works.
My own personal preference is that games like this have some VO, but not a huge amount. Think "original BG