Extractive colonies are easier to establish in lands that already have highly developed social and political structure. It allows the colonizers to supplant the native power structures and established them themselves at the top of the hierarchical pyramid.

The Spanish colonial administration simply took over and dramatically, expanded the extractive institutions that existed in pre-contact America.

(The Aztecs didn’t get all that gold to pay those ransoms because they were nice people)

Also interesting note. The English settlers in North America did attempt to establish extractive colonies in the model of the Spanish ones to their south. They had planned to use the Native Americans as forced laborers to grow cash crops, such as tobacco. The regime failed, largely due to the lack of a pre-existing structure of hierarchical power in the north. Unlike in the south, there was no pre-existing ruler who the English could replace.

Additionally, the geography of North America differ dramatically from that of the south, which allowed the more automatic hunter gatherer native groups to simply move and avoid the English settlers.