Atheism vs. God's Existence

[Mister Agenda]

I am curious what some compelling reasons are for becoming an atheist. What are some reasons that have been the deciding factor?

It seems to me, judging by the large number of versions of "there's no evidence" one-liners, that many people who identify themselves as an atheist espouse some sort of positivist argument:

Positivism is a philosophical theory stating that positive knowledge is based on natural phenomena and their properties and relations. Thus, information derived from sensory experience, interpreted through reason and logic, forms the exclusive source of all authoritative knowledge.[1] Positivism holds that valid knowledge (certitude or truth) is found only in this derived knowledge.[2]

Verified data (positive facts) received from the senses are known as empirical evidence; thus positivism is based on empiricism. https://en.wikipedia.org/wiki/Positivism

However, there are a bunch of problems with this philosophy so most atheists' arguments aren't very sophisticated. BTW, the same thing happens for theists--many do not have sophisticated arguments for their belief--relying on experiences and trust in the contents of their holy book(s). 

The question of the existence of God cannot be commented on by science--not at all. These are metaphysical questions and reasons and arguments for and against the proposition are necessarily metaphysical in nature.

You have days when you're quite the little asshole, don't you?