Not incredible, rather the only thing that is credible.
And not just retail workers, they are only one of the canaries in the coal mine.
>Why hasn't economic progress lowered work hours more?
Because lowering the work hours of laborers who provide more profit by more hours worked, over the short run or the long run, was not the intention of allowing economic progress to begin with.
The ones employing those workers are supposed to benefit by increased leisure time for themselves, not reduced hours for the workers, even when financial rewards are more liberally dispensed across the board as economic progress occurs.
The purpose of the US Federal Reserve was to better control economic progress not for the benefit of workers or the general citizenry, but for the bankers themselves, largely those in the Northeast with the oldest money. This was particularly important to them after major deposits of precious metals were discovered and exploited in the west. (Which is one of the major reasons why SV is where it is.) Hard currency or especially gold when the dollar was based on it could not have been allowed to continue to be held by working citizens or the potential power shift could have been too much to enable the growth of their capital gains to continue to outpace labor.
Before the Federal Reserve took control, economic progress was much more out-of-control in a way that was not was as bad for workers who in bad times could still always work for subsistence, compared to pure capitalists who were subject to non-increasing gains, reduced gains, or gasp actual losses even when they were in what was supposed to be the least risky investments.
After decades of control and supposedly harmless gradually increasing financial incentive for laborers, union power became too great anyway by the early '70's so Nixon & the Fed put a stop to it by inflating the currency in a way that would never had been possible if citizens had been allowed to retain gold or hard currency. Gold was for banks only for decades up until that time.
Gold could only be re-allowed to the public after it was fully decoupled from the dollar.
They don't want you to work for mere subsistence (especially on your own farm or business) nor allow enough collective wealth to accumulate among the workers, since either extreme reduces the incentive to put in as many of the hours which lead to Wall Street profits.
This trickles down right through SV to any new company whose ultimate outcome is an IPO through a Northeastern stock exchange.