You must know that this is just as much a fallacy as many others.
The notion often presented as being true is that because there are so many examples of any particular phenomena therefore it/they must exist, even if so many (perhaps the majority) are falsely identified as such or are fabrications. This applies to such things as sightings of ghosts, UFO sightings (tied to the existence of aliens), after-death experiences, and many others. But this is a fallacy. All can be untrue just as much as the majority can be untrue, and what people believe is irrelevant. Much like a religious belief supposedly being true because so many believe in such - and all the other religious beliefs are untrue. And much like religious beliefs, many will interpret their experiences differently (and often wrongly), given that there are so many different religious beliefs, and that we are all human with the problems that come with such - being prone to making errors in all sorts of ways. Apart from this of course, and which contributes to the issue, is the belief that one's own experiences are reliable, that how one interprets them is so also, and that such reinforces what others have to say concerning any experiences.
And all of the phenomena mentioned, and no doubt others, do have people who have interests in promoting their existence, and will do whatever is necessary to do so, but where those requiring proper evidence usually will not be so biased or have any particular agenda. For example, there may be aliens and they may visit but the evidence for such is not so as to make this obviously true, despite the amount of 'evidence' - it not being good enough. And a bit like the existence of God, for many.