Because he's an extraordinarily good actor playing the only Trek villain whose name means a thing to the casual moviegoer.
Whatever cavils long-time Trek fans may have about the casting are beside the point; we're all going to pay to see the movie (well, except for that one guy over there who's about to post "I have no interest in this/I'll see it for free/I'll wait for the DVD").
Lord Garth, FOI wrote:
Why are so many people POed that we are getting one of the finest, most intense, dramatic actors in the world playing a version of Treks most beloved arch villain ?
Why does the phone always ring just when you're taking a bath?