Lol... Interesting to see the different reactions to the "involuntary bodily noises" from various cultures around the world! Narrowing down on the sneeze - here, I find most just use a half of that reply - "Bless you", instead the full "God bless you"; more of a reply habit than meaning anything...
When I first saw your username, thought it said Achoo.
Was about to say "
GodBless you". Lol Jk jkTrue. But, really, a blessing can't exist without a god. So it's always implied.
Again, though, god is kind of beside the point. If people said, "You are sure to win the lottery!" when people sneezed, it would be just as silly and worth changing. :)