Why Study ?!

Today what I'm basically gonna do is study, study and study :/ but why ? why do I study ? what am I gonna do with these grades? Well I've always wanted to be a pilot, on the other hand my mom have always wanted me to be a doctor, but being a pilot doesn't require high grades and I'm pretty sure I don't want to be a doctor!! So why am I studying? do I do it just to gain knowledge? or to make my mom proud but then crush her dreams when I tell her I don't wanna go to a medicine school? Why am I studying? I still have no idea.