This, as I take it, was because all human beings, as we meet them, are commingled out of good and evil: and Edward Hyde, alone in the ranks of mankind, was pure evil.
The true meaning of the story. Each person has both good and evil inside of them. Dr. Jekyll was at one time able to control the evil within him but over time the urges were too intense and he gave into them. At the end, he was both inwardly and outwardly both good and evil.
