The medical system will disagree: all doctors should work 30 hours straight with no sleep, else they're not real doctors and slacking off.
Most doctors become doctors either as a childhood dream or to fulfill the expectations of others. Lots of pressure at an early age - and it only intensifies from there. Getting the grades, pre-med maybe, certainly biochem, then med school.
Residency is the home stretch to a lifelong commitment, feet don't fail me know, brass ring almost within reach...
Maybe it would be 'better' if that wasn't the case, but it's simply what is.
(Not saying startup culture is good in that regard. Just saying it has less of a life-or-death impact on others.)