Start with machines. A non-automated worker can produce a certain amount of product. An automated owrker can produce more. But the worker didn't create the increase. The automation investment did. And unless demand for pencils goes UP, the demand for pencil making labor HOURS goes down.
One can argue that culturally keeping women out of the workforce was unfair, and I agree. But one of the RESULTS of that was that the single wage earner family structure fixed the labor force at 50% of the physically fit adult population. And this resulted in a certain BASIC supppy and demand equation for the value of an hour's labor.
The REASON why half of the able bodied adults in the society didn't work for income doesn't matter. It limited the labor force and this DOES unavoidably impact the value of an hour's work.
Now, starting in the 40's (but offset by certain other factors like combat losses among men), women started entering the workforce. Of course it didn't happen overnight. It took DECADES. And over those DECADES, the labor force grew steadily in realtion to the population from roughly half of able bodied adults being he workforce to almost all able bodied adults being the workforce.
This has INEVITABLE impacts on the supply/demand equations that determine the value of an hour's labor.
If the DEMAND for work is not nearly doubled while at the same time nearly doubling the available pool of workers, it WILL create negative wage pressure.
And since wives going to work didn't result in the household buying an extra house and an extra house full of furniture, etc... it did not match the increase in demand for work.
Again, it does not matter WHY half of able bodied adults were not a part of the workforce BEFORE. All that matters is the inevitability of the downward wage pressure that INTRODUCING that other half into the work force.
IMO folks complain that it is somehow unfair that we have transitioned from a single wage earning family economy to a double wage earning family economy. And I get that it feels that way. But it is an EFFECT, not a cause. The CAUSE of this transition is essentially doubling the workforce while at the same time greatly increasing the efficiency of the individual worker WITHOUT increasing the demand for the goods and services provdied to ENOUGH of a degree to keep the value of an hour's work high.