Managers run stores, hotels, etc. Managers expect you to work since you've applied for the job. Managers may make things hard on you. It doesn't mean they're a straight up dickhead but this is how jobs work. You apply for the job, you do it.
Stop generalizing. Not all managers are mean, but they do have to make the hard decisions sometimes that you may not like because believe it or not they are responsible for some of the shit going down there.
Power trips or stress. Shit a desk and paperwork would make me mean too. Blah nooo