If someone loves history, geography, social sciences and is really strong in it, why do they need to do all the other crap?
I'll give you the same answer I give my students when they say, "Why do we have to learn this?"
It's very simple. Our nation depends on civil-minded productive citizens, and public education is an exercise in developing, strengthening, and disciplining the mind, very much like regular weight training does for muscles or general exercise does for the cardiovascular system.
Are you going to have to use all, or even a majority of, the information you learn in school? Heavens, no. But you'll be a more civil individual who behaves in a civil manner, which is a very necessary and productive requirement for the welfare and maintenance of our society.
It is certainly up for debate what information is necessary, or how it is presented and "exercised", in order to be successful at this endeavor. But there is no question that public education's primary purpose is not for an individuals rote memorization of facts as much as developing civil minds for the preservation of our nation.