Such a surface level explanation. The real answer of course is politics. The railroads know the government won't let them shut down for even one day, so there's no reason for them to negotiate in good faith. So they negotiate in bad faith. Why would they give into labor demands when labor can't strike and their customers being big businesses won't substitute away in the face of political controversy?

Every large company would rather make more money than spend more on labor. Railroads are in the unique position of having the government break their workers strikes.