I work a job where I'm covering other shifts a fair amount as well as working doubles. I also do not get Holidays/any extra days off. Prior to this I was in a salaried corporate middle management job, so for the past 20 years I've worked 55+ hours a week on average. I can tell you that for this particular job, yes, their goal is to destroy your health so that they get a few good years out of you and then you'll leave because it's too hard on you. That way they never have to worry about paying their workers (outside of a small percentage with high fortitude) wages that are much above baseline.