Father Benedict Groeschel wrote a marvelous book on the subject, and I think every discussion about apparitions is better informed after taking what he had to say in mind.
One thing that stands out in my recollection (I no longer have the book handy) is that the overwhelming majority of claimed apparitions are really not. The numbers of claimants run into the hundreds but the public is hardly aware of most of them. If one didn’t know this one might assume that the number of reported apparitions was quite small (and the percentage of non-approved ones was only some portion of that) and those two assumptions would make the likelihood of an apparition one experiences or knows about seem all the more probable.
In other words, one might think “it hardly ever happens, it happened to me, it must be real!”
For some reason or another a few of these get more legs than the rest, and do receive a popular following to some degree, but that does not make them any more genuine.
The actual number of approved sightings is very very small compared to the number of reported ones.