I spent a little bit of time responding to each of your questions with why I think they're much less harmful to an employer than pretty much anything an employer can do to their employees. But I realized none of that point-by-point stuff really matters, and deleted it all.

An employer can systematically destroy an employee's life and finances if they pull the right levers. In places like the US, employees are often terrified of getting fired or laid off because they'll lose their (and often their entire family's) health insurance. Companies use this (and other leverage) to give crap raises, make employees jump through ridiculous hoops to get promoted (and then deny those promotions anyway), "encourage" employees to take the bare minimum (or no) time off, etc.

And employees have to eat it all, or risk losing their livelihoods. Let's think about that phrase, "losing your livelihood". The fact that it's a common saying really tells us all we need to know. Employers hold the power. If they're caught doing bad things, usually there little to no penalty. Employees sometimes do sneaky things (all those things that you mention) and eventually get fired and/or sent to prison.