I worked as an engineer for many years. So, here's my conclusion. The answer, which I suppose I would get from math instructors, is this. You may never need it, but it teaches you to think. Decision trees taught me to think.
Decision trees are useful.
Geometry is not. I wish I had learned about the real differences between males and females when I was in high school. That would have been really useful. Geometry is not. I wish I had learned about statistics and probability in high school, so that I could have been able to distinguish between truth and twisted truth.