I agree that it's surprising that (1) working long hours seems to have been found ineffective in academic studies and yet (2) businesses tend to want it.

Since when did businesses behave according to perfect economic rationality, untainted by macho complexes or status displays/contests?

I think I've seen something very like this offered as an explanation for investment banks' punishingly long hours: one of the things an i-bank's clients are paying a lot of money for is knowing that at any time they can call up the person who's trying to put together a deal, and discuss it with them. That means that those people need to be around for long hours, which means that the people doing analysis for them also need to be around for long hours.

Think what you might do if you were actually trying to make sure someone was awake and on-call for discussing a deal at all hours. To my mind, redundant staff or shift-work would function better than espresso-driven manias.

Whereas I've heard plenty about I-banking hours being a form of hazing, which makes perfect sense.