Well, Dawn has weight maps and still uses two neck bones. I guess they wouldn't have rigged her in that way without a reason.

If you see the images above I clearly see a reason to have more than just one neck bone.

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.