Isn't it very important for machine learning?

Aerial Imaging. We use it for both photogrammetry and some aspects of image color correction based on its histogram. I imagine its used extremely often in robotics as well.

when you say “this” do you mean the content in the linked book or linear algebra? because the linked pdf doesn’t have much to do with linear algebra.

The entire field of computer graphics

I think set theory, at least, has something to do with database querying.