One reason I don't believe in God is intellectual. I am not at all convinced by the arguments given for God's existence by the Theistic philosophers, neither the cosmological argument & the design argument nor the 32 other specious arguments favouring God’s existence, which to a person not science-savvy might be plausible.
A second reason I don't believe in God is emotional. I am comfortable with not having answers to everything. By temperament, I have a high tolerance for ambiguity and uncertainty. Many people become cognitively dissonant with uncertainties and probabilistic world models, and thus they feel the need to close that loop with a definitive answer, regardless of how intellectually indefensible it may be.
This low tolerance for uncertainty in many others probably has an evolutionary origin related to the fact that in the Paleolithic environment in which we evolved, it was almost always better to assume that everything has agency and intention. That is, there would have been a selective advantage to adopt the default position that other people, animals and even inanimate objects in the physical environment possess agency (capability of acting) and intention (acting in a manner that can affect you).
Making Type I errors - False positives (assuming something is real when it isn't) will not take you out of the gene-pool because they only make you more cautious though paranoid, but making Type II errors- False negatives (assuming something is not real when it is) can result in you being too high a risk-taker and therefore a meal for an animal like a Sabre-toothed tiger that really does have agency and intention.
Because of our Theistic Ancestors making a Type I Error (False positive) in their lives, they survived and gave birth to their children who in turn gave birth to their children and after virtually infinite such reproductive lives, we were born to enjoy whatever joys & pleasures there are in this world. One price they had to pay was that they became Paranoids & God believers. So belief in God(s) in our Ancestors was absolutely essential for them to survive and parent our direct ancestors. Thank goodness for that or else we wouldn't be talking about all this now.
But times have changed
We no longer face the kinds of environmental threats that our Paleolithic ancestors faced. We can now afford to get deconverted and give up belief in God(s), Heaven, soul, eternity and such illusions and still lead a moral, productive, compassionate and meaningful life.
If religion as we know it today disappears from the face of the earth, what will occupy its place, and what will the consequence be for our quality of life? In a post-religion world, the time previously devoted to religious rituals will likely be taken up by sports, popular entertainment, and social networking. Everything will seem much the same but there will be very little public trace of formal religion. Despite the radical loss of religious ideas and influences, the developed world will be recognizably the same! Yet, there will be one important difference.
With a sharper focus on solving practical problems - as opposed to the emotion-focused strategy of organized religion - the quality of life will improve more rapidly. Instead of the unhappy world of the past where misery, want and disease were prevalent and inescapable, we can anticipate a much more prosperous - and much happier – future. In that future, living conditions will be so much improved that organized religion can no longer find a market for its services.
What's our role in bringing about this transformation?
It might take another 500 years for the whole world to be Godless, but it is inevitable considering the progress that the various sciences have been making in diverse domains. But it is not necessary for the entire population of 7 billion humans to deconvert to skepticism & secular humanism. It needs only a few leaders spread out throughout the world to convert to humanism, who then can conscientize the masses.
You as parents could do your bit toward nurturing such leaders of the future. Even if you cannot teach your kids introductory Cosmology, Evolutionary biology, anthropology, Evolutionary psychology, Neurological study of Supernatural phenomenon, Comparative religion (as history of human fantasies & not as facts) & How to Live meaningfully in a Godless world, yet you could contribute to this future by not forcing your kids to worship imaginary deities and when they attain teenage, encouraging them to read appropriate literature or explore web sites on Secular Humanism to become enlightened,