Not sure how serious you are, but I'm not at all surprised that they wouldn't be interested in promoting something that, while infinitely better than smoking cigarettes, still involves the ingestion of an addictive, mind-altering substance.
Yes, so is coffee, and alcohol, and many others - even chocolate. (The "mind-altering" part anyway). But I'm not sure there's even a "World Coffee Drinking Day", or a "World Beer Drinking Day", or if there were, whether or not Google would choose to join in the celebration.
(Now let the flaming begin).