Mr Silver wrote:
It's the same reason why each of the new actors in the roles of Kirk and co. were chosen as much because of their resemblances and similar features to their predecessors, as their talent.
I think that's overstating the resemblance. The only one who really looks a lot like his forebear is Zachary Quinto, who bears a startling resemblance to a young Leonard Nimoy. Chris Pine looks somewhat similar to Shatner, Karl Urban bears a broad resemblance to Kelley (allowing for the different eye color), but none of the others really look much like the original actors beyond having approximately the same ethnicity.