As far as I know, ghosts are not bound to the Earth forever, and after a certain amount of time, they eventually reincarnate. Ghosts are the souls of people who have already died physically but still have something left to say. Some didn’t manage to convey something during their lifetime, and some may be filled with anger or resentment, which prevents their soul from finding peace.
Some of them for traumas, this is also another reason for why rape is so detestable, other than all the negative aspects that comes from it, some souls are so damaged and traumatized that won't reincarnate, and they end up dead on the astral.
But a ghost is far from being tantamount to a soul let alone to an astral body. A ghost I for one is either an etheric body of deceased person while a spirit is their mental body which have split when they passed away. We are reincarnated through the soul not through the subtle bodies. Nevertheless the ghost that can be seen are on the akasha. Akasha can be easily seen and felt. Even though I am far from being advanced or intermediate in this path I can attest that someone I know has been on a certain common place recently just by reading the akasha. Akasha is what we use to read and see past memories or events thus akashik records.