There are advantages to having a good poker face at work.
When you are working for a toxic company, it can be tempting to give them a piece of your mind before making an inevitable swift exit. Truly, it is astonishing how many employers believe that they can treat their employees like garbage and get away with it. The natural reaction is to be outraged and point it out as soon as you possibly can.
However, there is a reason that we are told to keep our friends close and our enemies closer. When dealing with a company like this, it can pay to put up with their behavior just long enough to be able to collect evidence on the unethical practices that they pretend are OK. If you play your cards right, it could be exactly what is needed to expose them and, with any luck, shame them into being better.
This is not a foolproof strategy. Plenty of people suffer through terrible jobs and never get the opportunity to tell it like it is with their former employer. Still, those who do get that opportunity offer an invaluable service, allowing job seekers to avoid disaster and enabling current employees to fight for better.