Ghost sightings can cover a wide range of clothes and that is generally because ghosts wear whatever they wore when their mortal form died. The concept of ghosts dressed in white gained prevalence at a time and place when white linens were rapidly becoming common for the average person. The industrial revolution increased the supply of white linen clothes, also white linen bedding, both at homes and in hospitals. Ghost stories gained popularity during this era, which was also a time of growing world population and growing deaths in densely populated areas. This intersection is why ghostly appearances very much fit the description of a nightgown-wearing tuberculosis patient. During the Victorian-era in Great Britain, the medical field was advancing rapidly, so a keener awareness of life and death coincided with customary dress/fashion of the time to produce stereotypical images of ghosts and ghouls.

The white sheet alludes to a burial shroud.

Intellectually the leap to believing in ghosts at all is longer than the mere stutter step to believing then in ghosts' apparel, ghastly accoutrements, and ethereal monocles.

But surely an identity would need to projected onto a ghost to transform it from an unknown haunting in a sheet into a known phantasm recognized by its victim.

Like dimensional digital projectors from our soul or collective consciences onto the sheet to create a ghost seems to be the idea.

Great. After reading that headline my subconsciousness is going to put a whole new weird spin on my nightmares.

All the times an apparition has appeared to me, they were dressed as people.

I just somehow knew they were a spirit.

Its happened a half a dozen times or so for me, since I was a small child.

I always wondered what’s their energy source?

Also when people see them that means photons have had to bounce of them and into the observers eyes. The same goes for the sounds they make, they need to move the air molecules for sound to travel.

Or could it be that it all just happens in the observers mind?

But that doesn’t account for poltergeists.

Any qualified psychologists in the house?

Because this is the color of the natural phenomenon that started the idea of ghosts, a pale white form floating in the dark in total silence seen out of the corner of the eye... a barn owl.

That lead us to a more interesting question, why barn owls are not black?

"You're an adorable little ghost..." https://jimbenton.tumblr.com/post/764044329102852096

Of course ghosts wouldn't appear naked, we can't see beyond the veil