In The Conquest of Bread Kropotkin talks about the massive productivity gains of Europe in the age of steam and steel, and uses numbers to show how there's enough beef and mutton and bread and chicken to go around and enough trains to get it to everyone who needs it, such that we can look forward to a future where a worker gets much more for much less work. And we have hit that in some respects: a chicken is nearly free now compared to its historic prices, and the 40 hour work week was not widely established when that book came out. So we work less and get more now, but we don't work a few hours a week in exchange for a life free of any economic insecurity, as has always been on the horizon for technology optimists.

Not an economist but I've heard the argument that the 5 day 40 hour work week was only possible by the increased productivity that came from the industrial revolution.

My understanding of the argument is that it doesn't deny that unions and strikes weren't instrumental but that it was only economically sustainable because of the increased productivity.

I believe Ford pushed for the 40 hour workweek in the 20s, so... yes, at least once :)

Since most of us weren't still working 19th century style 14 hour shifts in factories, or toiling with mostly manual labor at the farm, but had like 9 to 5s / 8 hour work weeks it was.

It was actually, but that was an aberration of the post-war period.

yes, between about 1948 to about 1973, real hourly wages rose approximately in lockstep with worker productivity.

Yes, with the formation of unions. The owners realized that they needed to placate the workers because damages were worse for business. So workers won a 5 day work week, 40 hours, and many more benefits.