In Macbeth why is it significant that Malcolm names everyone Earls?

He was borrowing from English feudalism (due to his conflicts with the same, notably the Earl of Wes) and may have been the first Scottish King to bring said feudalism to Scottish life. Can't remember if this is covered in Macbeth textually (I last took Shakespeare at OSU about 25 years ago), but it was probably well known among the target audience of the time...