Why are Ghosts Only Seen by Certain People?

I've been doing some thinking recently about why ghosts seem to appear to certain people and not to others. Some individuals claim to see spirits frequently while others often go their entire lives without ever having an encounter. Here are a few possible theories I've come up with as to why this might happen.

1. Some people might be more emotionally or psychically inclined to be able to see ghosts. Perhaps they are tapped into other parts of their brain that not everyone knows how to access.

2. It may just be a case of being in the right place at the right time. Perhaps ghost are more likely to appear in certain locations, and people who see them are those who frequent those places.

3. People who claim to see ghosts are making it up, for any variety if reasons.

4. Ghosts may only appear to people they have some sort of connection with or to people they think can help them.

Do you have any theories about why ghosts seem to only be seen by certain people?