https://en.wikipedia.org/wiki/William_Stewart_Halsted
Tldr, the doctor that came up with the medical residency program was an absolute coke-head and apparently expected everyone seeking that MD to work accordingly.
Fast forward to today... cocaine is a bit better controlled, but that seems to be about all that's changed lol.
I'm just a surgical tech, but from practically day 1 seeing what our medical residents go through struck me as 1) this is slavery, and 2) this is super, SUPER unsafe for the resident and any patients that get within arm's reach of them. What the actual fuck!