One group runs a gauntlet of fire by sleep deprivation during pre-med training: with on-call work hours up to 120 hours a week. And the other group are typically on shift rotas so their sleep patterns are permanently disrupted.
I'm going to call it for them being oblivious to the sleep requirements of ordinary human beings, because these professions are self-selecting for sleep-dep survival traits; only people who can work insane hours make it through hospital medical training, and only people who can take shift work in their stride make it as hospital nurses.
(Also, my observation of hospital doctors is that anyone you see on a ward outside core office hours is relatively junior, i.e. aged about 22-35. Senior consultants and professors work normal hours like everybody else. As for the nurses ... my understanding is that ICU nursing burns them up.)
(Source of observations: former hospital pharmacist here, who just got a refresher course c/o a relative who spent three months on an acute stroke ward this fall.)