Why is horror media relating to using cameras/camcorders such a common trope?

With movies like the ?Blair Witch Project, ?Paranormal Activity and games such as ?Outlast and ?Fatal Frame, its no surprise that the idea of using cameras in horror media is common. But why is it such a common thing to use as a story-telling mechanism? Why does it captivate people? Do you think its over-redundant?

Common thing because it gives the feeling of "this actually happened" since it's not all great cinematography to capture the movie.

I think because it puts the viewer in the drivers seat. Though it is done often, it is not done well.