You get what you reward
I see this all the time. The biggest reason all this happens is that management rewards this stress inducing behavior and worse, punishes those who don't work themselves to death. The guy who works 90+ hours per week gets raises and promotions while the guy who clocks "only" 50 hours ends up getting the pink slip.
At Apple, they even had a 90+ hour "club" complete with T-shirts. Yeah, that's the company that was run by that god, Steve Jobs, that you at Tech Republic all worship.