Possibly they were too consumed with Allie's battle with leukemia to pay Holden his due attention. As a result he is underachieving to gain their attention, or possibly as a means of punishing himself because he feels unworthy of love since his parents didn't give him any. He could also be trying to punish his parents for neglecting him. Other characters are certainly less than admirable, if he will let you write about them instead of Holden. For example, some people see something less than innocent in the attachment between Holden and Phoebe.
Many people seem to think so.
He sees nothing but death, grime, and squalor in general because his mind is clouded wioth the memory of Allie. His parents are either just plain bad parents, or maybe he was denied his parents' attention, especially his mother's, during a crucial stage of development. Possibly they were too consumed with Allie's battle with leukemia to pay Holden his due attention. As a result he is underachieving to gain their attention, or possibly as a means of punishing himself because he feels unworthy of love since his parents didn't give him any. He could also be trying to punish his parents for neglecting him.