Only certain dice may be used for certain situations. A set of dice must be stored in a particular container. And heaven forfend should you touch these special dice!
There could be other reasons for this. I think the whole touching of the dice and storing them in a particular container may not be superstitious as just cautious. Certain dice do have different roll habits. Saw an interesting video about how not all dice will roll the same because of the way they are made, so you will have some dice who roll 20 more often than 1 or something of that nature.
