My feelings on this.
1.) Comfort. Feeling like the universe is running according to some kind of plan, even if it's one we don't understand.
2.) Morality/Ethics. In some cases, this includes belief that only religion(or specifically) only their religion can impart moral behaviour, while in others, it's a moral code people feel is important for at least them to follow.
3.) Peer Pressure/indoctrination. The culture around you and/or the people who raised you believe in something and raised you with the belief as well. For a lot of people, that's more then enough to keep believing in something. Either because they were raised "This is the way things are" and still believe it, or afraid to discard it because it means rejection/exile from family/culture around them.
I've watched a lot of atheist talk show content over the years, and these 3 points are some of the most frequently used to explain a person's belief. They will often not realize it, but their answers, when directly asked about why they believe what they do, often boil down to "it makes me feel good." or "because if we didn't believe in god we'd all just go running around raping and killing!" and of course "it's what I've known my whole life."
They are very often incapable of actually realizing the flaw in their reasoning for believing these things, and not others, particularly when confronted with it, and retreat into shit like "you know in your heart you believe in jesus" or some other stupid evasion line. I've actually had this one to me personally at least a dozen times, when I've tried to explain why I am an atheist, to the utter bafflement of the religious people around me. Along with "why are you angry at god?" which is about as logical of a question as "why are you angry at the easter bunny?"
I'm not a sociologist/anthropoilogist but I imagine it would be interesting to see studies on childern who are raised without religion(while not explicity forbidding religion) and allowed to decide later in life(say, reaching adulthood) vs kids raised in a particular religion.
A study to determine what? Because I mean, there are studies like that out there. All kinds of studies about the differences in societies that are heavily religous vs not. You'd have to narrow down what result you are interested in though.
OT: Fandom. I understand it, but I still don't get it. I mean, the overwhelming obsession with a particular thing, to the point where you use it as a framework for your own personal identity and worth. Where you freak out and lose your shit just SEEING a person associated with the thing you like, feeling compelled to dress just like your friends like some sort of voluntary cult wardrobe. Defending and fighting others that have a varying opinion from you, to the point of hostility and bullying tactics. Just, all of it. This last is mostly what I've seen in teen girl fandom, from my own personal history as a kid. I remember distinctly, the girls in my middle school, being OBSESSED with the New Kids on the Block. And they would come to school, ALL wearing their favorite boy shirt, with purses that had pins up and down both sides of the arm strap. I even saw them out at a movie theater once, and they ALL had pillows with them, that had pillowcases with their favorite boy band member. It was this really disturbing cult behavior of sameness and devotion, to people they had never met. And it always thrown me off. And the adult version of it, things like the people who are basically a social bullying army for Beyonce, are along the same line of behavior.
And it's not just girls, but that particular flavor of fandom does seem to be common in young girls. Guys are just as bad, but in different ways. I used to browse a star wars related forum for several years, but stopped, because the level of actual religious devotion to that franchise, including schisms of doctrine (what is/isn't canon), interpretations of doctrine (is the Light/Dark Force stuff good/bad, were the Sith really evil, etc), and historical debates about details in the source material, and what it means (the various saber colors denoted levels of skill, and not just because their colors showed up better against certain backgrounds when filming) got so disturbingly real, that I just couldn't post there anymore.
