simple concepts.
Even if there was no God, the concepts of heaven and hell would still exist. Because we, as humans, feel the need to be validated. We can’t do good just to be good people. We want to do good things and be repaid for it. People want a prize, an award for being good. Heaven is just that. You get into Heaven, a place with all of your desires fulfilled, if you are good enough. No one will ever do you good without expecting something in return.
There is also this need to punish what is bad. Some people just need to feel in control. They curse you to go to hell so that they can sleep better at night. To feel like they have control over your fate and destiny. Other people can’t personally get revenge and just hope that someday, somehow, the ones that wronged them will be punished. And believing that after death they will be punished according to their wrong-doings, in a place such as hell, where they will suffer just like you did, brings people comfort.
Heaven and hell are just concepts that bring us security, comfort, they make us feel safe. Like everyone will eventually get what they deserve. Whether it is for revenge, to feel in control, or just a reward for our good deeds, people will always need the concepts of heaven and hell.