Theory: It's all about signalling commitment to investors. A startup doesn't produce anything until it goes gold on it's product or gets bought out by a tech giant who then takes their product to completion. So it has no cash flow at all until hopefully at the end a dump truck full of money pulls up and buries everyone in wealth. Up until that day, what pays salaries - what keeps your company employees from starving to death in the street - is investors who believe in your idea and your product. And while working a forty hour week for the duration (and telling your workers to bloody well lay off the coding at home) would probably get you more, better and less buggy lines of code added to your product per week, that doesn't really help you if it looks to the people funding you like you are treating their investment as a nine to five.
"Sophisticated investors should know better"? Eh. The only skill that actually matters to the long term success of a startup investor is the ability to pick startups with good product ideas. The kind of investor who is an expert on productivity and employee management is most likely picking investments based on those factors in some other industry where that is what companies live or die by. Meaning, an industry which is mature.
This of course implies that the optimal strategy for a startup is to pick a good product idea and then just flat out lie through their teeth about how many hours of work they do per week. Does it sound very implausible that a lot of the silicon valley culture of overwork is fiction? And some of it is naive people trying to actually work as many hours as people more cynical about investor relations falsely claim to.
Conventional wisdom, and many studies, hold that 40 hours of work per week are the optimum before exhaustion starts dragging your productivity down too much to be worth it. I read elsewhere that the optimum is even lower for creative work, namely 35 hours per week, though the sources I found don't all seem to agree.
In contrast, many tech companies in silicon valley demand (or 'encourage', which is the same thing in practice) much higher work times. 70 or 80 hours per week are sometimes treated as normal.
How can this be?
Are these companies simply wrong and are actually hurting themselves by overextending their human resources? Or does the 40-hour week have exceptions?
How high is the variance in how much time people can work? If only outliers are hired by such companies, that would explain the discrepancy. Another possibility is that this 40 hour limit simply does not apply if you are really into your work and 'in the flow'. However, as far as I understand it, the problem is a question of concentration, not motivation, so that doesn't make sense.
There are many articles on the internet arguing for both sides, but I find it hard to find ones that actually address these questions instead of just parroting the same generalized responses every time: Proponents of the 40 hour week cite studies that do not consider special cases, only averages (at least as far as I could find). Proponents of the 80 hour week claim that low work weeks are only for wage slaves without motivation, which reeks of bias and completely ignores that one's own subjective estimate of one's performance is not necessarily representative of one's actual performance.
Do you know of any studies that address these issues?