Nothing is ever perfect of course, but this is never a problem because these demanding clients always turn out to be capable of accepting reality after all. If you would make reality even harder and suddenly make it illegal for bankers to work at night, no one would be surprised to see deals still being done.
I find it hard to believe that working so much that your faculties are diminished brings something valuable to a job. It's more likely that this has something to do with social dynamics. It could be just a convention that was needed to please those who decide on your promotion, a way to signal your dedication, or a way to protect yourself against what others could do to you when you're not here. Finding a way to get rid of this would surely benefit all. This seems obvious now that one worker died of it.
> Deals are fragile creatures
So are we