Human beings only advance through collective knowledge from previous generations. It is a really amazing trait that keeps our species alive. In other words 2+2=4 to E=MC^2 is the culmination of thousands upon thousands of years of humans learning the previous generations' findings, advancing them, then dying, but passing the torch so we can improve ourselves.

If history were not taught, there would be no culture, understanding of the present, or contextual basis for which to base many societal decisions upon. Lawyers, historians, priests, teachers, curators, tourism, and many other professions would disappear.

Your question seems to be more along the lines of "When am I going to use this in life?" But the point of a general education K-12 isn't to teach what may be subjectively useful. If that were the case we would all be forced to learn math and science and become doctors and scientists. Instead we teach a base education to spark the interests of the individual which he or she may advance later in life. If not, that person at least has enough education (in theory) to know the current state of existence and how we have arrived at this point.