Like it or not, science is a job. The days when rich noblemen leisurely went after their scientific hobbies is over (and has been for quite some time). This job is not one you get rich on, at least not quickly. Postdocs, bearing the grunt of the work-load, earn on average about as much as a janitor per work-hour (survey results, PDF). The main reason for the low average wage are the long hours scientists put in: well over 50 hours per week (here and here). These 50 hours are the average (but the median doesn't fall far from it) and we all know the average postdoc will not end up in academic research: in 1995, 35% of science and engineering postdocs from the 1960s through the 1980s were in tenure-track or tenured positions in academia (source). Given the increased number of postdocs today and the decreasing number of tenured faculty, that percentage is likely to be much, much lower today.

Personally, I have received reviewer comments such as "6 papers in 5 years after his PhD is barely mediocre" and I usually work 60-70 hour weeks (until I became a dad, that is and the number dropped significantly to around only 50-55 now). Given that the scientific community is comprised of highly self-motivated, driven, smart people and not only publishing in 'high-ranking' journals is important but also to publish many papers there, we have the perfect storm for workaholics: a surplus of talented, motivated people who not only do their very best to perform high-caliber science, but a community which expects not a single shot, but a stream of high-profile publications. Average is not even close to sufficient any more.

Obviously, you may argue that more brain also means more gain. However, given similar intellectual aptitude, the candidate who uses their brain for longer hours will also have more gain. Thus, the only evolutionary stable strategy is to maximize your work hours to outcompete as many of your competitors as possible, because you never now how much is enough.

Productive excellence (or the quantitiy of quality*) is the norm against which young scientists today have to measure themselves if they strive to stay in academia. This probably means that successful candidates working less than 60 hours are the exception, rather than the rule. And who wants to bet their livelhood that they are exceptional?


*Of course I'm not implying journal rank here!