You know, this one’s hard to answer for a teacher: “Sorry, sir, why do we have to learn about that?” or even worse “Really now, why does my kid have to learn about that?”
Any honest reply involves knowing, or at least guessing to a certain degree of probability, how the life of the pupil in question will turn out to be.
Not even mothers can do that properly.
So, the question is a non-sequitur. That’s it. There is no good answer to it, until you realize that the whole of your education is more than the sum of its parts. It’s the perspective, the confidence that comes with a whole body of knowledge. Why anybody would consciously rob themselves of the opportunity of—well, I do understand it, of course, but it doesn’t make me less sad, when I hear The Question being asked.
In addition, some of the parts of that “body of knowledge” are rather cool, whether you need them in your later life or not. Here, watch woodworker/engineer Matthias Wandel explain, of all things, the Venturi effect like only a woodworker/engineer can: