I am sure we all have more than one reason, but what is the main one for you?
Truths don't obey borders, religion does. If Einstein could, almost by himself, think up accurate laws for the universe. How come humanity as a collective can't do the same with any god/deity? It doesn't hurt my father was raised atheist and my mom was agnostic (but is now born again Christian)
I came to the realization that faith is no virtue--it is, in fact, a piece of bad code. Having lost faith in faith, the spell was broken, and anything that relied on it disintegrated.
The contradictions in belief. "God is all knowing, loving, and eternal." Yet "God" gets pissed off when humans "don't behave" in the examples of the Great Flood and Sodom and Gomorrah. So, God/god is not above human emotions. The christian god doesn't sound any better than the Greek gods.
The distance between what we do know and what we don’t isn’t a justification for a deity... it’s the reason for living our lives.