That may be the case in the City (I have images of interns jumping from City skyscrapers in the back of my mind...) but not in the general labour market in my experience. Generally speaking, unless you've committed to something, screwed up, or contracting (£$£$), then you generally leave at the end of your shift or working day. However, I am genuinely intrigued why you think this - could you elaborate? Maybe I'm overworking without even knowing it.
I do work in an investment bank, but it's not a case of interns throwing themselves out of windows. It's more a case of "I'm a professional, and I gave my word I would complete X by a certain date, and if all that takes is a couple of extra hours then I will stay and complete it, rather than be unreliable."
