The main reason I feel people avoid admitting paranormal occurences is the link with mental illness that they wish to protect themselves from ridicule.
My youngest sister wants to further her studies at uni studying the link between religious beliefs and paranormal happenings historicly and mental illness. I also find this link interesting so much. My brother blocks out paranormal no matter how blatent as tricks of the brain which he sees as incredibly complex and not understood. Do you agree on the grey area that illness and paranormal beliefs occupy?