Our various mythologies do seem to reflect some aspects of our known universe.
There's an obvious nastiness to reality. Its not that surprising that we came up with 'god-fearing' religious beliefs. This is the realm of mosquitoes, after all.
Mosquitos are just a pest, and even when they spread disease, it affects a minority of the world's total population (although it still is a lot of people, yes). (And if the mosquitos could talk, I bet they would complain of the humans that destroy their nests when able, and kill them while they attempt to get food for their eggs...)
However, the universe does seem quite hostile, more often than not, to human life. This is looking outside of this world, at the cold harshness of space, and the cold reality of a universe that really doesn't care one way or the other what happens to you -- unconscious, yet ultimate, forces of nature.
However, even then, cold and dangerous reality seems to have little concept of the infinite. I can't think of anything in the universe that can be expressed by infinity. Yet many religions not only has the concept of the infinite, but also infinite life, even after our material core has ceased to function.
What's worse, some religions have the concept of the infinite life in punishment. Can you imagine hearing an annoying noise for years on end? What about decades? Centuries? Just sitting there and hearing this annoying noise, no matter what you do. This ringing, that you can't put out of your head, that you can't just ignore, that swamps your thoughts so much you can barely think or concentrate on anything for too long. For years... and years... and years... and years... and years...
That's just an annoyance. Imagine torture for such a length. Searing agony, burning that never dies down, pain that never fades, never allowing you to concentrate, or feeling anything else.
Now times the amount of time by 10, and keep doing that. You can do that millions of times, and you're still nowhere close to infinity. You can multiply a googolplex by a googolplex by a googolplex, and you're STILL nowhere close to infinity. Infinity has no number, and cannot expressed in any way that truly resembles anything in human experience, or as far as I see it, much experience of the universe. It's truly INFINITE. It's not just multiplying googolplexes together; it's multiplying an INFINITE amount of googolplexes together. There is no end to it.
I think that the greatest reason to assume an infinite amount of punishment, is that the average human truly has no understanding of the term "infinite". It's this awesome thing, and they recognize it as such, but they still don't get it.
The cold universe is far more merciful than any such a concept. The cold, uncaring universe is actually far more merciful than an omnipotent being that cares so much, he tortures you if you don't do as he says.