Check out below turntables of some of
characters in Inc. When approaching the book, some characters were
modeled and painted in full 3d, while others were only modeled, with
textural details painted in 2d on a per image basis, and others
existed completely as 2d paintings.
A fully modeled and textured character takes weeks to produce, and so this level of detail was reserved only for characters we'd be seeing again and again, in lots of final images. In these cases, it was worth making the extra effort up front, because the process of making the final images would go a lot faster with a full 3d character.
If the character would only be seen in a couple of final images, a 2d process was used which is far quicker, but less versatile.
Since Inc and Landis were each going to be in dozens of images, it made sense to go the full monte on our two main protagonists.