Five reasons slaves were used in the colonies

1) slave labor required for farming and tobacco cultivating
2) Plantation and farm slaves tend crops and livestock
3) Few men on domestic sites
4) engraved in society - tradition
5) some southerners believed they were helping the slaves, had dehumanized slaves enough to think they could not function without slave owner help

first three are from google, try doing some research if you need to expand but here are some general topics you can dig into :))