This was done to maximize the profit of the colonizer.
Step-by-step explanation:
European governments supported the policy of mercantilism instead of free trade with their colonies to maximize their own profits at the expense of the colonies and to not let them grow as economic powerhouses on their own.
Mercantile systems excluded the people who did the business in native countries from the profits they must have deserved, instead it was the profit that was taken back to the colonizer along with the product that was produced for them.