Richard Dawkins, a famous atheist philosopher stated that “There is no body that out lasts the soul.” He is a famous monist who believes that the soul is not real but if it was, it would not be immortal as it is connected to the body. He self classifies himself as an atheist and states in the opening chapter of "The God Delusion":
"God is a delusion. ... Human thoughts and emotions emerge from exceedingly complex interconnections of physical entities within the brain. An atheist who believes there is nothing beyond the natural, physical world, no supernatural creative intelligence lurking behind the observable universe, no soul that outlasts the body and no miracles - except in the sense of natural phenomena that we don't yet understand.” There are many people that hold this view.
Many people believe that there is no soul because if there is no God there cannot be a soul. They believe that a near death experience it may be your brain being starved of blood. When you're dying, your brain only uses its most vital functions (keep breathing, keep the heart pumping, etc.) which is in the brain stem near the occipital lobe of the brain. So in near-death experiences, blood goes straight to the back of the brain where the brain stem is attached and, if there's enough blood left over, the occipital lobe. So your brain will see something, but your brain doesn't have enough blood to tell you what it is you see. Therefore your brain only recognises a white light. This is what will allow atheists to deny the soul as science is able to prove it wrong.
However it does not explain how in near death experiences people can retell and see everything that is going on.
In the society we live in today there are many religions that can be contradictorily to each other due to their belief about God and the soul which is another reason people do not believe in a soul. Another popular view is that consciousness is an emergent