Talk:Age of Empires III: The WarChiefs/@comment-26459635-20170429235801/@comment-2602:306:CE29:B0D0:E1DA:237B:1868:FC3C-20191219123201

The fact that the expansion is named "Warchiefs" means that it's primarily focused on tribal chieftains, not massive native empires. They could have easily done an entire expansion on the Latin American empires, and another expansion on the North American tribes, but instead they tried to combine the two, and this is the result.

Also, I think because the Incas were featured in AOE2 (along with the Aztecs) they wanted to add in some new civilizations, rather than just recycling old ones.