Belief cannot be proven. There's always wiggle room or a way out. If a lightning bolt hit a non-believer as they did something bad and was followed by a heavenly voice of chastisement, he can explained it away as UFO-caused, mother-in-law caused etc.

I once pointed out to an atheist that statisticians have estimated the likelihood of our enormously complex world's existence as 1 chance in 10 billion(?)

His response was "yeah but there's still a chance"

It is BECAUSE G-d's existence cannot be proven that believers will receive reward.

When everyone finally becomes aware of HIS existence, its too late.