Several people in this thread are trying to find a reason for these practices, but at the end of the day it's just abuse. I started my career in an analyst program at a different investment bank several years ago. People pile their work onto you and your boss doesn't do anything about it because he doesn't want to piss them off. And they abuse you when they have a bad day. In my first three weeks of work, I had one guy threaten to punch me in the face for looking at him. Another guy was worse...he smashed his phone on the desk about two feet from my face to "show me who is boss," occasionally got physical with me, and would routinely say stuff like "I own your soul" to me while I was working.
Sad part is, the abuse happens to everyone so you start to accept it. I saw my boss's boss get publicly humiliated by his boss's boss a couple times. Difference is, the junior guys don't have anyone to whom they can pass off work that rolls down to them, so they just end up doing the work of several others on their team. They're the backstop.
There's no profit-oriented reason for the culture, just like there's no good reason for prison abuse. It simply manifests due to the nature of bullying in a hierarchical culture that rewards imbalanced personalities.
Sad part is, the abuse happens to everyone so you start to accept it. I saw my boss's boss get publicly humiliated by his boss's boss a couple times. Difference is, the junior guys don't have anyone to whom they can pass off work that rolls down to them, so they just end up doing the work of several others on their team. They're the backstop.
There's no profit-oriented reason for the culture, just like there's no good reason for prison abuse. It simply manifests due to the nature of bullying in a hierarchical culture that rewards imbalanced personalities.