One explanation would be that the causation is the opposite: watching the business succeed makes people excited and so they start doing longer hours because the

One explanation would be that the causation is the opposite: watching the business succeed makes people excited and so they start doing longer hours because they mistakenly hope that will make things go better. Working at a reasonable, sustainable, pace requires big discipline. It's hard for a computer game studio with a release coming in 12 weeks to stick to 40 hours because that will get them 12 great weeks. They'll tend to slide into 80 hour weeks in panic but end up doing less. I think two real issues are that you can't compare against a control version of the company and you can't tell you are slowing down because you are tired. Another issue is management. Most managers think hours in means more productivity out, it's hard for them to not fall into that seeing as it is so widely held as true.