I think a more interesting question, which is touched upon by several posters including Triggaaar, is 'why do people believe in' (false notions and concepts like) 'ghosts'?
In my view, the answers are the same as the answers to (from my world) 'why do people believe that targeting process X...
Why would I feel the need to have an explanation for unexplained phenomena? At my age? I loved all that stuff when I was a teenager (the occult; Borley Rectory; Aliester Crowley; Erich von Däniken; Uri Geller). Later I grew up. The natural world is hard enough to explain without worrying about...
How confident, exactly? Confident as in 'confident the Albion won't be relegated this sason' or 'confident I will win the lottery...eventually' or 'confident I will live forever'?
I thought the question was about ghosts of people, which clearly don't exist. I am not sure whether prawns have ghosts, but fish certainly do. Back in the 70s, supermarket chicken was described, in Private Eye as 'tasting like fish ghosts that had been incinerated off Bikini Atoll'.
Made up stuff does 'exist' though - as fiction. The things you list are real TV programmes. Time travel, reincarnation, clairvoyance and god are all made up so they also exist as fiction. I think the OP is asking whether ghosts exist as real things. Obviously they exist as fiction. Especially in...