Here are a few reasons you may or may not agree with.
1-Religion is a holdover of superstition from a time with limited scientific knowledge that we have since grow out of so it no longer has any value in our lives.
2-Religion is a tool is a tool that was and can be used to control the masses.
3-Religion contains valuable lessons like fables to aid people in their journey through life.
4-Religion is a profound truth that if understood leads one to a correct understanding of reality/the universe.
5-Other. A different reason for why religion exists which doesn't fit into any of the above. Please explain.
Religions still exist because the philosophy of science ignores a large block of valid natural data. The Philosophy of Science is connected to group verification of phenomena, through the five senses. This approach and philosophy limits science to the material world, since the five senses are connected to the material and chemical worlds.
For example, if a group of scientists were in the woods, and the heard a sound in the darkness, the sound might be verified by all, but the various theories for the source of the sound may not be verified by all. That is the line in sand. It would up to each scientists to try and prove their theory so all can see the source. Then that will be inside the line.
This approach, although very useful, cannot fully address internal consciousness data, such as dreams. Science knows dreams do happen, but we cannot see another person's dream to verify all the details. These phenomena are real, but are outside the scope of the Philosophy of Science. It is like what each scientist thought they heard in the woods example; internal overlay to form a theory.
Dreams and visions are often associated with religion. These are genuine internal data of natural information. Science is not up to the task, based on the material limitations of its philosophy. Religions deal more with these internal experiences, connected to the brain's operating system. Some aspects of science approach this, but it is still called soft science, since some data and effects are not easy to reproduce; unique data.
The analogy would be like looking at a data disk, that is coded in a computer language we do not know. We can analyze the disk and all can agree it is made of glass. We can even display the code, but it makes no sense; dreams, so we dismiss it is worthless and unscientific. Religions by being so old, and through meditation; dwell on internal data, helps learns to understand some of the coding, such as the value of command lines like prayers.
Being able to see things, science cannot see; coding, looks like magic. But it is really due to the brain generating data to help translate itself; projection of a map of the within. Mythological systems were often maps of the brain's firmware; Apps, which define human nature, at a given time in human conscious evolution. The age of the Titans was different from the age of the Olympians. Human consciousness changed along with the changes in the projected maps; apps.
Out of the empty space of Chaos came Gaea, the earth, Tartarus, the underworld, and Eros, desire. Gaea gave birth to the mountains, the sky, and the sea. She took her son the sky, Uranus, as her husband, and with him, she mothered the twelve Titans, the very first gods and goddesses, taller than the mountains they used as thrones. However, Uranus was disgusted by their next children, the three cyclopes and three monstrous sons, each with fifty heads and one hundred arms, and he threw them into Tartarus, the underworld prison of suffering.
Yet Gaea loved all of her children, and she could not forgive Uranus for his cruelty. She made a diamond sickle for her youngest son, Cronus, and with it he defeated his father. Gaea later married her son Pontus,
the ocean, and the Titans took charge of the universe. They were the ancestors or parents of most of the
twelve Olympians discussed here below, though it was through their children that they too were eventually overthrown.
This very first symbolism is about the evolution of the human ego or human secondary center of consciousness. From chaos; formative years, there appears the earth; POV for sensory reality, plus a POV for the under world or the inner world of dreams. Eros or desire appears to have been the drive behind the original ego about 5-10K years ago.
The ego offered a secondary reference. On the outside we see through the eyes of the inner self; desire, and also inside we see the inner self as separates from the ego; dreams. Adam and Eve in paradise, was where all desires were instinctively fulfilled. I am not going to go play by play, but the evolution of these gods; the changing map, reflect the interaction of the inner self and ego and the development of advancing brain firmware apps, that underly evolving human nature; inner self and ego. Science sees superstition, I see brain IT.