"Ah, Bartleby! Ah, humanity!"
The loneliness outside provided no motivation for Bartleby to leave the work place. He would work in a forlorn job to survive in a forlorn city, (the narrators’ description of Wall Street being desolate) for what reason? Only to be forlorn and then die? So he sits and waits. When death is the final result and the act of life is despairing and work itself is despairing (which is what must be done to ensure life) and neither seems to be anything other than woefulness feeding woefulness to end in death. Bartleby just waits for death. Nothing in-between can be enjoyed and there’s no use in accomplishing the task. Which also explains how and why he dies in jail. There was no escape for Bartleby, outside of work: despair. Work itself: despair. With or without despair the final result is death. He simply waits.
The narrator feels sympathy for Bartleby and feels sympathy for humanity, himself included, even though he is stronger than Bartleby, he understands.