Instead of those employees getting jobs with different companies, they brought this to the attention of the FedGov who wasn't friendly with Bill Gates at the time.
The thinking is that a person isn't allowed to freely choose to be someone else's slave, nor is that person allowed to freely choose to be someone's indentured servant.
Contracting for a single company for an extended period of time and not being treated as an employee appears to some people as a form of indentured servitude.
You may disagree, but FedGov is becoming all powerful. If all you have to do is run a few jobs for some other shipper, rather than hoping that you'll get your way via the courts or some form of work stoppage, then maybe that's a better alternative.
I come from a family that does contract work. I also do contract work. If I don’t like the work, leave. People depend all thier money and take out loans, then find themselves “indentured.” These are not the days of the company store. The government is not helping, but is part of the problem.