Something even more prevalent than the knowingly fictional stories of ghosts are the ones that are defiantly non-fiction, the sort which have been rendered dubious by our culture of cynicism and, well, all the phantoms we see onscreen and in the pages of books. Anecdotal evidence isn't enough to sway a hardline scientific skeptic - and nor should it, lest we start believing the testimonies of otherkin - but there's been so many first-hand sightings and experiences of ghosts that you can't really ignore it, or suggest they're all just hoaxes, hallucinations, or people unable to tell the difference between a semi-transparent human being and a dusty lampshade.
Everyone and their dog has a story of a time they encountered something paranormal, whether it was a simple feeling of dread in their home or coming face-to-face with a fully-fledged phantom. There's been multiple explanations given for this, from the hallucinations and optical illusions from before and even mass hysteria, suggesting that a significant percentage of the population is plain crazy-go-nuts. Which seems more of a stretch than just believing in ghosts, to be honest. Would you rather we were a species that frequently invents stories about otherworldly beings, often without even realising it, or that life after death is real?
Again, the reason anecdotal evidence is so rarely relied upon is because it's subjective. The appearance of ghosts, like black holes, cannot be repeated in laboratory conditions, or even be relied upon to pop up where you claimed to see them originally. When somebody tells you they saw one, you have to not only believe them but also their critical faculties, senses and the like. All of that said, we've built up such a huge library of subjective data at this point that surely, eventually, it passes into something a little more objective? Like, how can there be these many instances of people seeing ghosts and there not be something to it?
Of course, when you look at it that way, you have to start thinking the same way about other stuff. Like people who claim to have met Bill Murray. Or aliens...