Is there a reason why the villains of "Atlas Shrugged" don't want to live?

Toward the end of Ayn Rand's novel "Atlas Shrugged," Hank Rearden and Dagny Taggart realize that the looters do not want to live. Does it make sense to ask why that is -- meaning, why don't they want to live? In other words, is the question so basic that a reason cannot be given for a person's answer? If a person can answer it, what sort of reasons can a person have for choosing to live or not? Moreover, can that choice be rational or not?