Productivity is not a linear function of working hours
One popular misconception that's ingrained in our society is the idea that productivity is a linear function of working hours. Even at a scholarly level, it was generally assumed that the more hours you revised, the better your exam result. There was even a maths module where they stated "A person's performance in a piano exam can be expressed as y=mx where x is the number of hours per week the person practiced for, and y is the exam performance..."
The problem with the "productivity = working hours x constant" is that it ignores two areas of inefficiency. If people are working longer hours, it only means they are sacrificing more time for their work, it does not necessarily follow that they use that extra time efficiently. People naturally tire out if they're working long hours (so when the relationship does hold, it's a diminishing returns curve, not linear). In addition, it doesn't take into account how useful the work is. Extra layers of bureaucracy, laborious methods of solving problems and finding useless extra work to fill in time with, results in longer working hours and more effort being put in, but no extra gain.
It strikes me that the social norm of rewarding and judging people for the number of hours they spend at work is rewarding them primarily for the amount of self-sacrifice they make, rather than how well they address the work, and to some extent encourages inefficiency (there's no reward for working efficiently as you still need to fulfill regimented hours regardless). It encourages the long hours culture, and the inefficiency has the double whammy of wasting employees' time that they could have taken off or spent doing more constructive work, while employers have to pay them for working inefficiently.
I believe that a good way forward would be to move towards rewarding people for their performance and effort applied, rather than the number of hours they spend at work. Less of a need for regimented working hours and a pronounced rush hour, more scope for working from home, and encourages employees to work hard because if they work very efficiently they may get paid more and/or get extra time off. By reducing inefficiency we may be able to reduce working hours without offsetting productivity. Some work does physically require people to be around certain premises for certain hours, so regimented hours are sometimes necessary, but even in those cases, an element of performance-related pay can sometimes be smuggled in.
I wouldn't advocate abolishing working hours altogether though- we'd need to be sure that everyone was getting a fair workload under such a scenario, and the easiest way to ensure this would be to give them an estimated number of hours' worth of work over a time period. Thus, people would still be expected to work a certain number of hours on average, but in many cases it wouldn't have to be as regimented as is the norm today.
The main barriers to the above initiatives being more widely used are, I think, the "productivity = working hours x constant" assumption, and as per usual, social inertia (the idea that a job should, by definition, mean working regimented hours in an office, because "that's the way it's always been done"), but there are signs of a slow trend in this direction.