tl;dr: the patriarchy. For the real reasons you'd want to look to the industrial revolution and Taylorism. PS. Women we're allowed to work when we standardize

tl;dr: the patriarchy. For the real reasons you'd want to look to the industrial revolution and Taylorism. PS. Women we're allowed to work when we standardized start times so everyone would arrive at their station at the right time. You can't run a mill with only half the workforce, so during the industrial revolution it was extremely important for everyone to show up on time. That's the real reason and it has nothing to do with men's inputs and everything to do with the needs of the means of production. Before that you started work as the sun rose because we had no need for standardized start times. The 9 to 5 thing is more an evolution of a whole bunch of inputs, the final input being primarily Henry Ford and the 8 hour day / 40 hour work week that finally allowed everyone to actually consume all the goods they were producing. That is up until now when production has again outstripped consumption. PPS. I really get annoyed with revisionist feminist history.