I think some ghosts may be doing their Purgatory. I don’t have an explanation for all ghosts, or even what they are.
My opinion largely depends on a single event.
Way back in my Presbyterian days, my prophetic old (Methodist trained) pastor said to me "I think you’ll be doing a cleaning job for a short time. You won’t like it much, and you won’t be doing it for long,
but I think the Lord will just want you to hear about a ghost." (Emphasis mine).
At the time i knew how accurate he was with his predictions, but I still thought that one was over the top. Basically I just ignored it. Now he died himself in 1992, probably made that comment circa 1990 or 1991, and certainly had no effect on the outcome.
Fast forward to 2006, I did a cleaning job for a short time (about four months), didn’t like it much, and “heard about a ghost”. The “ghost” was due to a former manager who committed suicide in a store I was cleaning way back in the 1960’s.
This “ghost” story also involved Catholic Answers Forums via an Australian priest whose bio was on the forum, the priest himself, and has followed me around since 2006.
I can’t be bothered telling the whole story all over again, but I personally think the “ghost” was the manager doing his Purgatory in the old store where he committed suicide. The priest said a mass for him circa 2010 (name uknown), and I’ve never been game to go back to the old store and see if he is still hanging around.
Strange things used to happen - the young bloke who was intially showing me the cleaning run didn’t like being in that store at night - he said one night ALL the stock on one complete row of shelves just jumped up and landed on the floor. At other times he could push a very heavy buffer with his little finger - something was pushing it with him (maybe the ghost was amusing himself scaring the young bloke).
The shop staff who worked there were quite sure the ghost was “alive and well”.
I wonder about the ghost ridden USS Arizona in Pearl Harbour. What you have there would be a large number of young men, killed in comabt on a Sunday without any real chance to prepare for it. What happened to them spiritually?
The following item may have a reality behind it, whereas most people would probably just dismiss it as imaginative interpretation of a photo. I certainly didn’t give ghosts much thought, until the old pastor’s prediction came to pass (and it took 15 years to even start).
mysteriousuniverse.org/2011/10/the-ghost-face-of-the-uss-arizona/