We, human beings do not seem to be something special in evolution. A dog has better sense of smell. Cheetah runs faster. Snake is deadly, so on. Every species comes with an agenda to preserve self and procreation. Several species learnt the benefit of staying together and hence society.
Humans developed skills like language, ability to think and awareness of self. We needed such faculties in the absence of other skills like running fast, and powerful teeth. With the ability to think, we explored nature as science, created social norms, went in to beliefs etc. The main purpose is self preservation. Well being of neighbour, society is very important if I have to preserve my life. Beliefs make people to ensure peace. Peace and pursuit of happiness is important for self preservation.
Life itself was an occurrence by accident in the chemical soup in nature, a concoction of many factors. Like an amoeba, or a tree, we arrive and go. Our intelligence, consciousness, conscience, understanding of science or self are all a product of evolutionary process. When we go, all the intangibles go. There is nothing in evidence for us to guess what happened to Newton, Budha, Hitler or the humble mouse after death.
It is very discomforting to think that we just disappear. Well, that is the purpose of beliefs in making people think there is continuity so that they behave properly during their time. It gives us a feel of goodness to assume more purpose in life than what can be deduced from gross evidence.
The question is, can't we be good just like that without needing the prop of beliefs. Beliefs like 'life after death' or heaven/ hell run the risk of justifying the suffering of life forms by assuming such miseries are result of wrong deeds in earlier births, or fore runner for happiness in future. The holocaust during World War II and death of tens of millions humans poses a question to any rational mind, did they all deserve such tragedy, all of them, children too; as much as you tread on the path of ants, and many die and some escape.
Law of nature, the grand design, gravitation, cosmic movements in galaxy, etc are more predictable than our humble lives.