> People used to fight for these rights. What happened?
Everybody got convinced that a) those rights will be used by those people who obviously don't deserve it and b) those rights will make life harder for them when they become billionaire business owners.
The US experiment with social democracy in the 1940s, which was not terribly comprehensive in the first place, has been slowly dismantled as the employer and political class continues to concentrate as much wealth and power for themselves as possible. Key to this has been to weaken and villainize labour unions at every opportunity.
When sick, you continue going to work until you wind up in the ER. If you're lucky, you don't get fired when you're there. Only exaggerating slightly. It's pretty sad.
As for what happened, the US isn't highly unionized outside certain regions and trades. Everybody else has next to zero legal protection. White collar workers typically get some leave simply by virtue of having skills that are more in-demand. And the labor movement largely allowed conservative, anti-labor factions to cast them as evil socialists. In the US, "liberal" has long been a bad word.
Never being able to take a day off for anything at all is incredibly harmful. People used to fight for these rights. What happened?