Not only this (which is super accurate in my limited experience with these types of jobs in HS/college), but that high turnover even among managerial staff mean

Not only this (which is super accurate in my limited experience with these types of jobs in HS/college), but that high turnover even among managerial staff means that really to advance at least a few levels in the organization, all it takes is 1) sticking around; 2) not being bad at your job (not even being really good just be decent). Hell, I used to be a dishwasher then line cook at a Friendly's (east coast family restaurant, primary PA/NJ/NY/CT/MA) for two years and by the time I left for college I was the most senior person there who didn't have a key to open the building. And two of the three cooks who had keys were still in school, one HS and one college. Managing a restaurant is super demanding work but it's not that far off from median salary. It's not as much of a dead end as people think it is, especially if you start at the bottom and work up.