After the establishment of the Jamestown colony in 1607, the British established other colonies in the Southeast primarily for which purpose?
All of the colonies were established as sources of cheaper raw materials for Britain, and as markets for the produced goods.
Colonies in that era were all about enriching the Motherland. The incentives to colonists included their own personal gains, but the balance always had to tilt toward the founding country.
It is the increasing demands of Britain on the colonies in terms of economic output (increased by taxes) that eventually led to the decision to revolt and become independent.