Dice have a lot of superstition that surrounds them. A player shooting dice might ask for someone to blow on them for good luck. And something one must never, ever do is touch someone else's dice without asking first. That is an offence of the highest order. Best to give everyone their own set.
The Extra Dice Pack for Cthulhu: Death May Die gives players a full extra dice set for their games. The pack includes three black Basic dice as well as five green Special dice. This extra set means players don't have to share as often, letting them keep the luck rolling on their own set.