They wanted to attain their innocence because they had practiced witch craft. I believe that is correct
Macbeth is considered by many a critic a Sakespeare's mature tragedy. The play contains a lot of supernatural elements and takes place in Scotland. Indeed, these traits do not appear by chance. It is well known that King James had a fascination for the obscure arts, there is even a book called "Daemonologie" written by the king himself.
The Scottish play, as it was called, begins with witchcraft. The lines where it is said that three "weyrd" sisters "All heil Macbeth, that shall be King hereafter!" (49, 50) reflects Shakespeare's intention to reverence his patron and his interest in the uncanny. It is of importance to mention that the word "weyrd" has its origin in the old English word for fate, which is one of the main themes and motifs in the play. Macbeth is to become king and face his destiny.
Macbeth's skepticism is present when we read in the words of Macbeth orders "Say from whence / You owe this intelligence? Or why / Upon this blasted heath you stop our way" (75-77). There was skepticism for what was to come with the new union. The term United Kingdom comes from there, from the alliance of the nations.
The play, with all its supernatural elements and references to withcraft and nobility, demonstrate respect and honor to the new king, who watched the theatrical representation of the tragedy and found the association to his interest in the dark arts presented in the Globe.
