I can't claim to definitively know the answer but I would imagine that even spirituality is not distributed evenly amongst humans just as intelligence, empathy and the like are not evenly distributed.
I think one's upbringing must play a considerable role. I imagine that being raised in a religious, fundamentalist family would make it very difficult for a person to ever grasp any kind of spiritual reality and perhaps families that did not encourage thoughtfulness, that is, to think for one's self and genuinely ponder the meaning of life would make it difficult.
I came from a card carrying atheist family but they gave me free rein to think and experience life my way and it lead me to a belief in a God.
It also must be very difficult for a person who is somewhat educated to be confronted by religions claiming Genesis Creation is literal, the Flood of Noah is literal, martyrs of Islam get 72 virgins, and so on and so forth, one always wonders what crime the 72 virgins must have committed. And the endless would-be preachers who are so full of meaningless drivel, that is enough to put anybody off God and religion for life.
Not to mention the likes of the despotic conmen such as Benny Hinn, Jim Bakker, Jimmy Swaggart, Creflo Dollar, Kenneth Copeland, Joel Osteen, Joshua Mills and hundreds of others who are some of the most unnecessary people on this planet.
All of these corruptions of religion must inoculate people from ever accepting spiritual concepts and God. Religion is its own worst enemy.
Then there is the anti-science sentiments of religion. This is a scientific world and educated people are not going to accept dogma and superstition over evidence. As a consequence the baby goes out with the bath water, or God in this instance.
Then there is the endless waring of religions. The countless millions destroyed in the name of God. The almost complete destruction of indigenous cultures all over the planet in the name of God and conversion to Christ.
There is a very dank and ugly swamp of religion to wade through before one finds anything meaningful in religion and of course religion in a sense owns God. They have the copyright.
I think its amazing that anybody in this age genuinely searches for meaning and God rather than taking the soft option and joining one of the many junk religions.
