Ambiguity

Exactly why does Bartleby always "prefer not to"? Why can't he make friends, or communicate? What's at the heart of his rebellion? Why doesn't he quit and get a different job?
Why does the Boss have sympathy for Bartleby?
What else in the story seems open to individual readers' interpretation?

Bartleby refuses not to because he has lost all motivation and emotion to do anything. It is the only thing he says in the entire story. When people try to talk to him or get him to do something, it's always the same line. The thing that ticks off the people the most is that he cannot give a reason as to why he keeps saying he prefers not to. His heart is at rebellion because since he used to work at a dead mail place his heart became broken. He was so heartbroken with all the dead mail he received that he gave up on life. He probably does not want a different job because he might feel that loss of emotion again. The Boss holds a lot of sympathy for him because he understands. I believe he understood how Bartleby felt and it allowed him to feel sympathy towards him.