(Most)Shitty job conditions can only exist if there is an abundance of labor; why can fast food joints get away with irregular scheduling? If the supply of labor is tight, jobs have to add bonuses to keep workers.
Why is health insurance tied to jobs in the US? Because during WWII, the government set limits on wages so companies started adding insurance and other items to attract workers.
During the GFC, what did companies do after cutting workers? Start cutting benefits, the workers couldn't walk since no one was hiring.
Look at pensions, they went away in the 80's. If you google why they went away, the answer is 401k became availible, however: https://en.wikipedia.org/wiki/Early_1980s_recession
> Even the “father of the 401(k),” Ted Benna, tells The Journal with some regret that he “helped open the door for Wall Street to make even more money than they were already making.” >Other experts agree: On its blog, the Economic Policy Institute recently declared 401(k)s “a poor substitute” for the defined benefit pension plans many workers primarily relied on, which provide a fixed payout for employees at retirement, and which have now become increasingly rare. Nowadays, “just 13% of all private-sector workers have a traditional pension, compared with 38% in 1979,” reports The Journal.
https://www.cnbc.com/2017/01/04/a-brief-history-of-the-401k-...
https://time.com/archive/6686654/a-brief-history-of-the-401k...