The ghosts that we see are not here to harm the Torrances but serve other functions: In Danny's case the Grady Girls warn him of the true danger, in Jack's case they serve to protect and serve Jack's ego in regard to his hatred for his family and his desire to be famous and "great", in Wendy's case they shove in her face the truth that she's been avoiding by various distractions/indulgences (books, television, smoking).
Specifically in Jack’s case, they occur in front of a mirror. No matter if we’re talking about Lloyd, Grady, or the woman in 237; they’re in front of a mirror.
In this image · No.4
The false optimism and the reality: Scene Comparison to No.62