And back when your boss might actually also be the owner of the company - especially through the 50s and 60s, the person you worked for in the factory very likely could OWN that factory, and so having a decent relationship with them made it easier to approach them with modifications that might make a worker’s day easier, without the hostility of a strike.
Now, since every company is basically owned by some conglomerate, looking to sell to some conglomerate, or is about to get swallowed by some conglomerate, things like “labor relations” are dead. You can’t talk directly to your boss about maybe making sure the factory line has proper guards in place, because the guy who he has to talk to in order to make that decision is having brunch in Paris or meeting with some world leader today. Even if they could, the company bean counters already ran a cost-benefit analysis that showed that the loss of limbs and the payouts and fines they’d deal with for having no guards in place would only be 34% of the profit they’d make from increased production capability or whatever.