Hmmmm Good Question....
To answer the original question:
I surmise that because most public places are around 70-73 degrees, and that the fact that the cold water is constantly running through the pipes and the housing in which the porcelain is made into, that it is constantly being sort of temperately chilled to a certain degree...
Also as we know porcelain is a very good conductor, and all these combined properties probably help to make it COLD to the touch being as we are 98.6 degrees 70 or less would feel cold!
LMAO...
Wow that sounds funny...