Eh, I'll spend a little karma. I believe the laws of physics, and it's the laws of physics which make the spontaneity of sandwich-appearance much less likely than the arising of homo sapiens based on billions of years of causality we have determined experimentally and then many many years of the very mathematical process of evolution. The big bang theory has some issues, but the idea that things were once really close together and now are expanding at an accelerating rate is pretty nailed down. Evolutionary theory is similarly nailed down, I believe both those propositions with a fairly high number of bits. I'm willing to admit I'm wrong, but not by merit of the possibility that I could be wrong. Not all possibilities are equal.
Can you point to some atheists who are as you say? As an atheist I've never considered this a particularly wonderful and full of life world (sure I like it and want to preserve parts of it but there's a lot of improvement to be made) nor have I considered the mysteries of the universe are incomprehensible. We are as Sagan said "the universe trying to understand itself".
You may say our lives coming into being by the known fundamental laws of physics is as unlikely as Santa existing, but here we are, the evidence is actually in front of us, humans and quantum mechanics. I've never seen Santa, yet I've seen humans and studied some QM.
Edit: oh hey, I almost forgot. http://lesswrong.com/lw/i8/religions_claim_to_be_nondisprova... "The earliest account I know of a scientific experiment is, ironically, the story of Elijah and the priests of Baal."