It’s not being rude, but merely non-superstitious, right?
Well, this is one instance where the title gives away the gist of my post. I don’t say “bless you,” when people sneeze. Ever. If I sneeze around others, I may say “excuse me” if the situation warrants it, but otherwise pay it no heed.
Now, aside from the obvious, religious connotation associated with the term, the more modern interpretation of it, is that the phrase “bless you,” in the context of sneezing, is a cultural meme; a superstition that has been superimposed upon modern society. Why is it a meme, you ask? You thought memes were just funny internet pictures? Read this article on The Uncommon Geek, then come back to this:
You read that? Good.
People are programmed to say “bless you” after a sneeze. No one thinks about why they do it, they just do it. I suppose most people think that they are being nice, but I personally find it annoying. To me it is about as “nice” as those drivers who insist on you go first through a four way stop even though they have right-of-way.
There are of course, varying accounts about how the term first came about. There may not be one single origin, and it is not impossible that several cultures adopted similar superstitions around the practice, that all eventually coalesced. One account claims that Pope Gregory VII first began saying “bless you” in response to the bubonic plague. Another possible origin is the ancient belief that the air in the body was somehow tied to the soul, and that a violent sneeze could accidentally expel the soul along with the air inside of a body.
Science, of course, has proven that to be rubbish. Even if we have souls in a spiritual sense, we obviously don’t lose them when we sneeze, otherwise there would be a lot of empty, soulless human beings wandering around this planet. Who hasn’t sneezed at least once?
I simply choose to not be superstitious. I like when black cats walk in front of me. I will walk under ladders out of spite. And I don’t say “bless you” when people sneeze.
FIN
After Terra 
I don’t always say bless you unless it was a really violent sneeze.Then I kind of say it as a way of saying “omg, you just sneezed six times!” But, if I don’t say it, people sometimes take offense. I don’t really see why, though. Seems like a pointless societal rule to me.