I have a number of friends who are presently in medical school who come from a wide variety of backgrounds. The ~75% number seems highly consistent with my experiences. Replace "coffee" with "adderall" and it would remain consistent. Some would say they would take adderall just to get the drive to continue their studies despite otherwise being stressed, burned out, depressed, disinterested, etc. as their end goal that they've been working towards for ~10+ years has been becoming a doctor.