I have a couple friends that went this path and one reason for the absurd hours seems to be that their work needs to be done in between the times the boss is working. A more senior analyst will hand off analysis to be done overnight or on a weekend, and expect it back the next morning. But there's also an expectation to keep up appearances / "be available" during the day. So they spend most of the work day either making work for themselves or doing nothing, then work their real full-time job after normal office hours.