The thing now is for you and people like you to delve into the question why some people insist that they peer into the spirit world by way of Ouija and get messages from the spirits there.
I cannot satisfactorily explain, theorize or even guess at how/why the broad cross-section of people who claim to be able to see and talk to spirits can do so.
Specifically related to the board, if we're talking about their belief that they're in contact with the spirit world - first I suppose it may be possible they are, but I don't think its related to the board except as a "focus", a concrete association that represents their communication, for them, which they could do with no tools if they worked on it.
But secondly, as to the actual BASIS for the belief in talking boards being gateways or devices to talk to the spirits, though some users including Iron Ghost will assert something similar to modern day boards are ancient, possibly dating back to 540 BC or earlier, usually due to things like the following:
The first historical mention of something resembling a Ouija board is found in China around 1100 B.C., a divination method known as fuji 扶乩 "planchette writing".[citation needed] Other sources claim that according to a Greek historical account of the philosopher Pythagoras, in 540 B.C. his sect would conduct séances at "a mystic table, moving on wheels, moved towards signs, which the philosopher and his pupil, Philolaus, interpreted to the audience as being revelations supposedly from an unseen world."
Source: http://en.wikipedia.org/wiki/Ouija
However, both of these claimed references are dubious, indicate a device completely different from a modern talking board, and are very rare if any such actual verifiable statements in these ancient works exists at all, so as far as my research has gone, I'm satisfied it is due to Fuld's repackaging, remarketing and widespread saturation of the boards among the public in the early 1900's, coinciding with the genesis of Spiritualism, due to the Great War. The prototype for Ouija boards was originally a psychic novelty that had nothing to do with ghosts, it was just a generic oracle like the Magic 8 Ball, but with the marketing change and popularity, it was inevitable it would be subsumed and associated with Spiritualist concepts, which mostly dealt with mediumship and spirit communication.
The other question is why some other people keep warning people to not continue in the Ouija activity and even to not get started at all, because they are going to get harmed in any way, from loss of peace of mind to real physical injury even death, or material disaster like traffic accident and fire engulfing their homes.
Since the 1900's absorption, the board has the reputation it gained as stated above, which is reinforced by the fact that people also have used them as youngsters, and mostly had bad experiences, plus, all these people, even if they claim atheism or wicca, etc. they or their families have backgrounds in some religion, usually a branch of Christianity, or at least they unconsciously, implicitly accept some of the superstitions of that religion as part of our culture, and carry them on, so besides bad firsthand experiences, their foundations are actually also pseudo-religious/superstitious at the very least.
Lastly, "friend of a friend" stories spare no topic, nor does the media, and no one wants to hear a happy story about something pleasant happening to someone; dark, dangerous, ominous, infernal, scary is what sells and gets retold. Brothers and sisters and parents relate stories they've heard, or their own bad personal accounts, and those people in turn propagate such stories, affirming their validity and sometimes misplaced/unquestioning trust and loyalty, with "it was my SISTER that had this happen to her so it MUST be true!" and so on it goes.
Then also why the Christian churches almost in total unison warn people not to get involved with the Ouija Board, because the Bible or God of the Bible is against the practice of any attempts at contacts with spirits of the kinds to be encountered by way of the Ouija Board, or other ways and means where materials and words and procedures enacted by humans are resorted to, to get to the spirits.
Of course the major religions like Christianity and Islam and also Buddhism even approve of and advocate communicating by prayer with spirits of the right kinds which these religions determine which spirits belong to the right kinds.
Right kinds of spirits are God, angels on good terms with God, souls of holy men and women already in heaven with God; for Buddhists they do pray to Buddha presumably already in a spirit state although in Nirvana whatever for all kinds of favors.
From the way you phrase this, I think you already know most of these answers. I can't speak with confidence about most of the other religions, but I know Christianity does indeed have warnings against dealing with spirits and witchcraft and divination and people that gibber and meep but will be of no consequence, which are all associated with the Fallen, since they're not of God and purport to give information or allow power through means other than God, which potentially weakens the belief's powerbase in followers. I have seen some assertions that the Witch of Endor summoning the shade of... Saul was it(?) was actually a demonstration of a demonic manifestation and deceit and was not actually meant to be interpreted as relating any divine message.
For related information and links especially to Fuld and the board, click my sig banner or go straight to the Fuld website's page: http://www.williamfuld.com/ouija1.html
Edited by Paranormalcy