I know I've posted on this before because it's a bit of a hobby-horse of mine. There's a fascinating analysis of long-hours culture in the game design industry, and how it is in fact counter-productive: Robinson on crunch mode
So, the thing is, it's well known in management theory circles that long hours cultures actually lead to lower productivity. So if the economics don't stack up, you have to ask what function the demand for long hours actually plays. And I think it's one of social control. By demanding long hours of your employees you are asking them to demonstrate that they put the company ahead of everything else in their lives - partners, families, hobbies. And, on a feminist note, it also functions as a handy mechanism of social exclusion - people with caring responsibilities (which, statistically, tends to be women) can't demonstrate those levels of loyalty, so get excluded, even if they're damn good at their job. It's another mechanism (like deals done on the golf course, or masonic handshakes, or - still common in sectors of the banking industry - going to strip clubs) which functions to exclude various groups of people, women in particular.