People believe in religion because it is indoctrinated to them by society and their families. People use it as a placebo to feel as if there is some greater purpose of this life. Instead of accepting that they do not know something, they prefer to create stories to supplement the lack of knowledge. Religion is a way to get simple answer that is not supported by any evidence without doing any deep thinking or analyzing anything. People also find that they can have a sense of security from having an imaginary/fictional being looking over them.
These are the primary reasons why people believe superstitious and fictional tales, also known as religion.
