Hallucinations are commonplace.
Optical illusions are commonplace.
Human brains are prone to "see" faces, and people, and animals, when in fact there is no face, person or animal present.
If two people (or a thousand) report a ghost, hallucinations are a possible explanation; Optical illusion is a more likely explanation; And
pareidolia is an even more likely explanation still.
In the absence of high quality and convincing evidence that a given report is not one of these three things, it might be reasonable to speculate about ghosts, but
at best this is wild speculation.
Wild speculation is fun, but it's not rational, reasonable, or justifiable.
Life after death is less plausible than perpetual motion machines, or rocks that fall upwards. If ghosts are your go-to explanation for witness reports of people who are visible, but aren't really there, then you are a gullible fool.
Which puts you in good company, as very few (if any) humans are
not gullible fools.