Plain and simply it's because the "sprirt world" exists.

There are millions and millions of people who have had experiences with "ghosts" or "demons" or "angels".

As long as people have these experiences...there will always be religion. People always looking to define what the spirit world is.

A self described Atheist will often change their minds about spirituality, once they come face to face with a paranormal incident. It happens all the time, all over the world.

The fac that there is a spirit world, is why there will always be religion.

IMO