The most important reason anyone is an atheist

[Sword of Christ]

Nobody has to believe claims which are based on faith.

The fact that there are an increasing number of atheists in (say) most of western and Northern Europe, with a trend being demonstrable throughout the west per se, surely highlights the failures of the religious messages in trying to convert and indoctrinate people and nothing else.

Christianity and faith in general is growing throughout the world in general though Christianity is on the wane in Europe. A lot of that may have something to do with state run churches.