Technological advances can't shorten the work hours because even in a society wealthy and technologically advanced enough that basic subsistence is available for free, people still struggle for zero-sum things, most notably land and status. Once a society is wealthy enough that basic subsistence is a non-issue, people probably won't work as much as they would in a Malthusian trap where constant toil is required just to avoid starvation, but they will still work a lot because they're locked in these zero-sum competitions.
That is the clearest explanation I've seen so far for this. (I've read a lot of SF, and asked myself the question.)
I don't think that's a complete explanation. I would say it's more along the lines of "If you start with somebody working a three-day week, it's much easier to employ them for another two days, than to hire a new person to work two days because that requires creating a whole new business relationship." Then both corporations and governments, I think, tend to be as inefficient as they can possibly get away with without dying, or maybe a little more inefficient than that. Work expands to fill the time available...
I would have to sit down and wri...
From Mike Darwn's Chronopause, an essay titled "Would You Like Another Plate of This?", discussing people's attitudes to life:
Conclusion, graphs, and references in article. As usual, I recommend reading Chronopause.com as Darwin has many good articles; to quickly link a few: