Several reasons.

Need for community is probably the strongest though.

Mainly because the idea is constantly reinforced in the children of believers from birth, from the very people they are supposed to trust the most - their parents, regardless of their ignorance. The result is compounded by confirmational bias, wishful thinking, and a hostile view to anything that doesn't conform to their taught ideology, so it's very difficult to break the generational cascade.

Though you'll hear theists say that the prevalence of their religion is down to the divinity of their god, ignoring the fact that their religion would certainly disappear into history if child indoctrination were to cease.

Same with Islam, Hinduism, etc
What you're born into is what shapes your worldview

This post was edited by Happypuppy on Jun 11 2017 06:39am

This is what I think. Regions have their own kind of comprehensive worldviews that reflect their culture and allow for the generational transmission of mores and folkways to younger generations. Religion is one institution to this aim, others being education, political systems, what is considered family, how we deal with death and the dead, health care, language, art....

Humans behaving in a social environment.

Quantum mathematics prove that there must be a "God" which I choose to view as a Great Architect. God is the ultimate software engineer.

I also enjoy saying dumb things about quantum mechanics.

Lol me too.

My favorite dumb things to say are non-deterministic interpretations.

And if anybody disagrees with me about physical determinism I need your cell phone to run some experiments. Gonna see how many times out of a thousand it doesn't dissolve in acid.

That's because you didn't vote for Vermin Supreme.

I did in 2012...