Mentat2020: Because having a celebrity in your game makes it less appealing? You make no sense.
Jorev: It's a waste of money.
Celebrity voiceovers don't enhance the game over an unknown voice actor.
Voiceovers does not require the skill that acting does.
I really enjoy playing Oblivion but I never thought the celebrity voiceovers enhanced the game.
In fact, you could argue that a celebrity voice detracts from the immersion of the game.
Ehh... voice acting is a talent still (after all, bad dubs can ruin a show)... but not to the point that hiring someone famous will make bad dialog better.
I can guarentee you that a good chunk of people bought this game because of Keenu Reeves. Does Johnny Silverhand need to be Keenu? No... does Keenu add anything at all to the character? Not really... but when you're making a game that is streamlined for the mainstream gamers you don't care about stuff like story or replayability. Just hype and "cool" factor.