I don’t understand why the population has to study quadratic functions. 99% of them won’t ever use it to solve their problems. Teach it to the 1% that’ll constantly use it. Teach the other 99% something else. Something they’ll use everyday.
Almost nothing in USA institutions has reason. Someone was probably tasked with designing a universal math curriculum and added it in, and it has been part of the curriculum for 50 years. We tend to think there’s a plan behind things, almost never is that the case.