I knew the first time I held aloft in my hand a warm, beating human heart. Upon beholding its ruby luster, I felt that I perceived all the intricate mysteries of our existence.
Wait, no, that was "The Temple of Doom." Why medicine? I dunno, I'd have to dig up my personal statement to tell you.
Some people are attracted to medicine because of the prestige a career as a physician carries, even in today's world. Other people are attracted by the challenges posed by one of the most difficult professional career tracts. Others are just stimulated intellectually by it while others think of it more as an art form. Some (much more than many here are willing to admit) think about all the money they can earn as doctors.