The forums are text
Books are text
a lot of things are text
A little bit of text would be fine in game or even a lot of text. I don't see a need to completely voice over everything in a game. Besides half the time my imagination of what a character should sound like is often better than what the characters do sound like when they hire a voice actor
Text has its proper place. As you say, a lot of books are text (excluding audio books, of course), the forums are text. Things like signs are also text. Text is great for getting a lot of information quickly. It is much quicker to read the forums than to have some audio record every message and play it if you click on a certain button. It is also quicker to read books than have someone read them to you. It would be dangerous to have signs not in text but have them broadcast at you. A stop sign is much better than a loudspeaker repeating the word "stop." I'm not saying get rid of all text. However, I think most gamers will agree the purpose of a game is not to get through it as quickly as possible, it is to have an enjoyable experience. Some people enjoy text dialog more than voice over. I do think, however, many people who say they want text over voice acting like text because it leaves more room and time for other things in the game - like more sidequests. I don't think the majority of people who prefer text over voice would choose text of voice if the game could be just as long and detailed with voice.
Text has it's proper place - when needing to gather information quickly.
Voice acting has it's proper place too - when trying to craft a mainstream and more realistic game.