My father is a urologist trained at McGill in its heyday back in the 60's, and they often worked much longer shifts than 24 hours. It was part of the training to be working while sleep deprived. In real life, a doctor often has to take calls in the middle of the night, and it was important for the medical school to either train students to be able to work under such conditions or be failed out if they couldn't hack it.

Mind you, they also had other traditions like working with cadavers with their bare hands only, out of respect for the people who had donated their own bodies.

Back then, it was expected that 2/3rds of students would end up failing out. Not just from long shifts, but the program was designed to be that challenging so as to weed out many people, to ensure that only the best would succeed. Nowadays, medical schools perceive the dollars spent training a medical student as too great of an investment, and want all their students graduate so failures are uncommon. Now once accepted, a student has pretty much made it even though the acceptance criteria is quite distanced from how they actually perform as a medical doctor. This potentially results in less qualified individuals becoming licensed.