"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" -Douglas Adams
I guess that's really the point, isn't it? Differing worldviews. Christians often ask, "How can an atheist look at the sky or a newborn baby, and not believe in God?" Atheists ask the opposite question about Christians. I remember a woman who considered herself a Christian saying to me, "Where do atheists think all the blessings come from?" Ah, the blessings! Christians can't simply be content with something good happening...it's got to be a blessing. Thus the recent trend of some people substituting "Have a blessed day" for "Have a nice day." It's apparently not enough to just wish someone a day that pleases them, or isn't horrible; they've got to be reminded of the blessings.
Meanwhile, a lot of atheists must wonder why Christians can't simply be content with appreciating the beauty of nature or a lovely day they're having, without bringing god into the mix. After all, when a Christian says that a pretty blue sky confirms their faith in god, aren't they really just saying, "I really like blues skies"? That's the goofy thing about religious beliefs. For the believer, there's just got to be a creator who made all this stuff, and since the only kind of sentient being we can seem to come up with is a human, we give it super powers. God is an omnipotent person, who has super powers, but other than that, is pretty much like us: he demands attention, he gets angry, he likes to make rules, etc. Differing worldviews.
The scary part of all of this is, you don't really have a lot of atheists demanding that their non-belief in god(s) lead to a bunch of legislation to curb others' rights; Christians, on the other hand, regularly demand that lawmakers respect their "values." Christianity, more than just about any other religion (except perhaps Islam), expects other people, no matter what they believe or don't believe, to live according to the values their god has decreed. So when those worldviews collide, there's not usually an agreement to live and let live. If there were, we wouldn't have so many problems about these differing worldviews. We could just say, "Oh, you believe in the Invisible Pink Unicorn? How's that working out for you?" And be done with it. Oh, if only...