I talked once to an ex investment banker who quit to move into tech due to the hours. He had lots of stories about ridiculous hours.
He said most of the time was wasted. It was spent on things like preparing slide decks for executives who then didn't read them, but who insisted the work be done in massively compressed time windows and then delivered by taxi at 6am on a Sunday. He viewed it as very inefficient and mostly a matter of bad culture. The senior managers did it when they were young, so they weren't about to let the next generation get ahead without the same sacrifices.
He said most of the time was wasted. It was spent on things like preparing slide decks for executives who then didn't read them, but who insisted the work be done in massively compressed time windows and then delivered by taxi at 6am on a Sunday. He viewed it as very inefficient and mostly a matter of bad culture. The senior managers did it when they were young, so they weren't about to let the next generation get ahead without the same sacrifices.