They were cheap. Meaning they wouldn’t have to pay a child as much money as they would an adult. They also weren’t big enough to attend school to get an education and they could also fit into tiny spaces adults could not.
This is part of an answer someone had to this same question.
Humans must have external constraints in order to live together
Answer: southern colonies were made up of mostly coastal plains and piedmont areas. The soil was good for farming and the climate was warm, including hot summers and mild winters. The growing season here was longer than any other region. The southern colonies' economy was based on agriculture
