Why can't everyone see ghosts?

[Stargazer]

Well, in fact, we all are able to see them, we just don't most of the time. Some people are more sensitive to spirits and their activity than others. There are plenty of reasons why our ability to see or hear them can be affected, and a few are discussed in this article:

theshadowlands.net/ghost/see.htm

Feel free to discuss the article below.