Why don't we use the [History|English Lit.|Chemistry|etc.] that we learn in school?
As a generality, isn't the math taught to most teens in public schools aimed pretty squarely at preparing them to take the standard calculus courses in their first couple years of college? If so, hardly surprising that most ex-students don't notice much use for that stuff in the real world.
And since the social function of that is usually to demonstrate that you're determined / focused / upper-class enough to successfully slog your way through it - gee, what would be the point to remembering or using it after getting your "made it through" bragging rights?