(By way of reminder, the following is in reference to my early life experience with a family that lost 3 children to a congenital birth defect. Each of the boys wasted away for several years, in such suffering that could only be characterized as cruel, if you actually believe God chose for this to happen to them -- particularly if you are a Fundamentalist who thinks God visits the sins of the parents upon the children. The parents were saintly people who could not remotely be categorized as sinners whose sons needed to be tortured and killed to teach them a lesson.)
Wow. It's stories like that that bring home the total uselessness of religion as a viable explanation for human existence. How can anyone glibly claim after all this that well, God really loves them and it was his will afterall? Such tragic events underscore the total indifference of fate and the universe to our lives. There is no loving being out there protecting us and blessing us with special favors. Life is a crap shoot from the moment you're born until you die. And all of human experience confirms this.
It must have been hard for ancient societies to accept that bad things could happen to them without cause. In the course of their development of superstitious explanations for suffering, sickness, injury and death, they must have come up with a pool of inexplicable causes which they tied up in a bundle and called God.
Like you say, life is a crap shoot, whether you talk about the biological processes that randomly mix to form gametes, and the subsequent randomness of fertilization, to the random way things can go wrong in the embryonic development, and from there all of the random ways infection and injury can ravage, maim, torture and kill individuals.
It would be easier to hold the Enlightenment view of the Deists, that there is a God who merely created the Universe, but who does not hang around after creation to mess with his little Frankensteins, wreaking havoc on them for arbitrary, unjust, angry and envious reasons.
The reason not to believe in God is not just that the model of God interfering with reality is so absurd. The reason is that all ideas of God stem from superstition.