There are possibilities of shitty company’s behaviour though: in case of said “envelope” salary, you still get some part of it officially (like minimum wage), so if the place is shitty enough, they can pay you only the official part, so you have a “not-so-paid” vacation. Or they come up with some reasons to not sign your vacation: “why July? Look at the schedule and better take February! We’re family and family needs you now!”
It’s not everywhere like that - usually low-skill and/or blue-collar stuff. But I encountered that in IT when I was starting out (and didn’t have much choise with tetail jobs in my cv)