[kevingadd]

Without mechanisms to discourage unfair termination (like unions and strong law enforcement), companies can and will and do ignore the law and just fire whoever they want. The threat of being knocked around by unions and/or the government for doing it is the only thing that stops companies from firing people when they get pregnant, or when they get diagnosed with cancer, or when they get engaged to their same-sex fiance, or when they adopt a kid from a foreign country, or when they report their boss for sexual harassment.

While you're waiting for your wrongful termination/retaliation complaint to wind its way through the existing systems, you don't have a job and you aren't paying rent. It's good to have multiple layers of protection so ordinary people don't get screwed by a business operator looking to save a few dollars.

fwiw the US's current government infrastructure is absolutely miserable at enforcing labor rights laws, so that makes unions a regrettable necessity no matter how bad they are. It'd be awesome if the country was in a good enough state to make unions no longer necessary.