Because these things happen all the time, including in Germany, and not just to immigrant workers:

http://www.equaltimes.org/exploitation-of-migrant-workers?la...

https://www.thelocal.de/20150602/eu-reports-widespread-abuse...

https://www.wsws.org/en/articles/2013/08/30/germ-a30.html

Because what the law says and what many employers think that they can get away with, isn't the same thing.

I thought unions were a form of collective bargaining to benefit the employee.

Surely they're not required to get an employer to follow the law. Isn't there a better way?

> Isn't there a better way?

Sadly not that I am aware of.

Either you go alone with a lawyer, or get some muscle beyond you.

For example, even for simple matters like vacations, many people are actually unaware what are their rights, benefits, obligations and how much control the employer has over them.

Many just take the simple route and believe whatever their boss tells them, instead of checking what the law actually says.