I am a medical student, and I have taken the MCAT. It is not just a memorization test. Each section is made up of a series of excerpts from scientific papers and questions that relate to that article. It requires you to synthesize the new information from an article with your knowledge of chemistry, biology, etc. to come to the correct answer. From what I understand, the USMLE exams are similar. It is important to score well on the MCAT because medical schools want student who are able to read scientific papers and apply their findings. Medical schools also look beyond just MCAT score and grades when selecting students.