There are certain functions that are so critical that people who work there are not allowed to strike and disrupt the economy. Railroads are one of them. Democrats tried to get them the best deal possible while also preventing an enormous economic recession which would have been the inevitable result of a freight shutdown.
I personally think those critical functions should be nationalized under government control, rather than having private companies reap the benefits of their special control, but that's a conversation for another time.
So far the working conditions haven't got that bad for enough to be noticeable, but at some point you'll have no new employees and the old ones will quit or die off.
I also think Democrats are happy to let them be the bad guys, while they make a lot of noise and token efforts to make things better, but never enough to hurt profits.