It’s because of big pay, highly mobile employees, hiding the real role of the HR and this false sense of security compared to the rest of the workplaces despite all these lay-offs from the big companies. Also, whenever a unionizing attempt happens, the companies go into crackdown mode and have their multitude of ways to either fire you with a bogus reason, remove your post citing “restructuring” or pulling you on a dead career track and demonize you in front of your colleagues with the usual “we care about our employees and everything can already be resolved through HR” speech. And moreover, many of these issues have a direct cause the Work Laws of the respective countries