Did you attend church as a child? Do you remember praying before meals? Did you listen to sermons and sing hymns?
Growing up, I did all of these things. Attending an all-girls Roman Catholic school followed by another all-girls Episcopalian school, I'm essentially the epitome of a girl who was born and raised into religion. Religion has always been a topic of massive interest to me, much to the dismay of my peers who would dislike when I asked questions about their religion and why they decided to chose that specific religion. Nonetheless, my co-workers recently had an interesting conversation that arose between the two of them: a Catholic girl, and a Christian boy (to simplify).
"I have to ask. Why do you pray through Mary and not to the Lord himself? What made you decide to be Catholic?"
Asked by the Christian guy, this question piqued my interest. And so, I sat silent and waited for the Catholic girl's response. After some short banter, there was no real answer from her. Out of respect for Jesus's mother? Because Mary has power? The only real conclusion that she came up with was that this conversation made her uncomfortable -- respectfully, as it would most people when their beliefs are challenged.
According to a 2015 Pew Research study of the changes of world religion, less than 1 percent of the 8.1 billion believers in 2050 will have switched into a new religion. But people don't just throw a dart to pick their religion or select one based off of its popularity (31 percent Christian, 23 percent Muslim, 15 percent Hindu, etc). Basically, there's a correlation between people and their culture.
So what?
This doesn't prove that one's religious beliefs are false. However, one's upbringing correlates with belief -- a cultural custom. This same idea applies to agnostics and atheists, the non-religious.
Children raised in a non-religious environment aren't atheists because they were taught to be atheists, but because they were not taught to be religious. In retrospect, a religion like Christianity has Christians because they were taught. If you were to remove religious books, tradition, etc, where would Christianity be? It would vanish. There is essentially no objective knowledge from which to rebuild it. 
People must join religions for religions to thrive. This chart shows that adults are not switching into new religions. So where are these additional religious people coming from? Children -- through childhood indoctrination. Religious adults have gotten their religion from their environment: families and friends. This is shown through the current existence of 26 countries that are 95 percent Muslim, and eight that are 99 percent Muslim.
Therefore, it is a reasonable conclusion to show a cause-and-effect because of such a high statistical correlation. Just like how customs, fashion, and traditional foods are cultural traits -- it seems that religion is culturally absorbed.
Thus, religion is like language. I speak Korean because my parents and friends speak Korean, and I was born in Korea. I also speak English because I was raised in the United States. Why do I speak Korean and English out of over 6,500 known languages in the world? Well, I didn't evaluate all of these languages before I picked the best one -- it was just a part of my environment. It's what I grew up with, so it's what I feel comfortable with -- naturally, those are my two languages.
English isn't any more "correct" or "better" than Italian, Chinese, or Farsi -- it's just what I became accustomed to as I interacted with my environment. It's not weird or "incorrect" to read and write Japanese in the United States -- it's just uncommon.
Anywho, back to my original anecdote. I asked the Christian guy about his beliefs -- would a person be damned if they were not Christian but lived and adhered to the moral teachings of Jesus?
"Yup."
Now according to all of these ideas I've presented -- your religion depends on your culture, which relates to where you live. If you do not live in a region where Christian is the predominant religion, the majority of the time, you yourself will not be Christian. Each culture has a different view of the world and universe -- a religious cosmology. So what happens then?
I challenge you to ask yourself: were you born into your religion?
