I once saw a really good YouTube video- which I haven't been able to find since, that explained that the concept of hell in the Christian religion came about at a very specific time...
Back in the day, the poor peasants working in the fields would be told that their reward would come in heaven. So- some decided to expediate the process and kill themselves. Why suffer doing back breaking work when elysium waits? Supposedly- it was at this point that the idea of suicides going to hell became prominant. The rich arseholes- including the clergy couldn't afford to keep losing their workforce so now- suicide was an option with utterly horrific consequences.
I really wish I could find more to back this up. Now and again I search but, draw a blank. Maybe someone else will have heard of this theory though and be able to flesh it out...
But in general- I'd just say- look at religion. Look at how closely it mirrors civil law. Do you suppose that's an accident? I'd say- likely not. Laws were presumably introduced to try and curb some of our more animalistic behaviours- stealing from one another- both money and spouses! Killing people that get in your way. Acting for personal gain all the time. Think about who those laws protect the most- the rich of course. Who's more likely to steal? Someone poor and starving or, someone rich who can make their money without risk?
Our religious texts were written (something like 40 years after Christ's death in the case of the first gospel) by people who could (obviously) read and write. How many poor folk do you think could read and write in those days? These people were obviously rich and powerful. Why shouldn't they have written these texts with a few things added in to help them out?
It's terribly compelling isn't it? If you're not willing to obey the laws of the land. If prison doesn't frighten you then, how about hell? It's a bloody good deterrent!
On a personal note, I'd like to add that I have doubts too though. I was brought up in a household which believed in God and heaven loosely at least. Then later, someone who did believe in hell and that suicides go there! So, I do sypathise how hard it is to shake those fears entirely.
Really though- it's not exactly a comforting thought but, I also feel like- God already hates me! God already knows what I think of them and I'm sure that alone is enough to be sent to hell. God seems to like devoted fans rather than people who question everything about them and their actions. So, quite frankly- if there is a God, I'm already screwed! Plus- honestly- I don't want to live in another place they had a hand in creating. I don't fancy going to heaven forever either- although, it would be nice to see my family again.