Why does macduff want to kill Macbeth himself?

What makes this part of the anecdote about elisa effective? when [elisa] finally walks home, after seven hours of standing at a cash register, her feet hurt. she's wiped out. it makes the reader trust the author as an authority on teenage issues. it uses emotional language to the reader experience elisa's daily challenges. it presents facts to support the long hours elisa is required to work.