The belief that shitty people will get what's coming to them through some external mechanism serves the useful function of allowing people to rationalize not engaging in settling scores and vigilante justice. I expect belief in the existence of hell to persist much longer than other "religious superstitions" (or whatever you want to call them).
I'd say it's a wash. Plenty of people who believe in hell do monstrous things, and plenty of people without this delusion behave as model citizens. Religious people constantly plead that without their belief system everyone would engage in wanton immorality, but this is just the self-reinforcing aspect of the meme.