The imperialists needed workers to work on the land that was colonized. The locals were not an option because they were often either insubordinate, or they were protected by the law. That's why having slaves to work in those colonies was great, which is why they got them from Africa.
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The Native Americans
Hope this helps
Answer:
Because the British East India Company had possession or Control on tea sales in the colonies and they still had to pay taxes on the tea