It's basically hazing. I doubt many entry-level IBers are in a position to ask their boss for anything, and they work grueling hours (even if it's inefficient)

It's basically hazing. I doubt many entry-level IBers are in a position to ask their boss for anything, and they work grueling hours (even if it's inefficient) to prove they have the willpower and drive to make it up the ranks in finance. So the IB isn't wasting money, it's actively selecting for the most dedicated/hungry workers.