A big part of this is how globalization has kicked the legs out from under the average worker and even the organized worker.
"There are some 12 year olds in southeast Asia that would be happy to have your job and work 16 hour days for $0.50 an hour, and you're asking me for a raise and fire escapes?!? Maybe I'll just move my factory over there and export the goods back to America. Don't let the door hit you on the way out, I don't want butt prints on my door."
If you aren't willing to put in those extra 4 hours of unpaid overtime every day, maybe you don't want your job.
Luckily, the worst abuses of this are easing off a bit as the labor market improves, but it's not going to go away.