I'm not talking about executives. I'm talking about rank-and-file office workers who have nobody reporting to them. Now, while there are probably some individual office workers treated worse than individual warehouse employees, the contrast is stark. Like, I work at the office of a factory. I don't have anybody under me, but the difference between how I'm treated and how they're treated is so stark. Hell, they're even union guys and I'm not.
Is there some obscure theory thing explaining this?
If any step along the production line stops, the whole system is disrupted. If no one's physically present on the factory or warehouse floor, the stuff doesn't get done. Manual workers are cogs in a machine. There's almost always more to do, so it's worthwhile to force every second of productivity from your employees.
Office work is a lot more flexible. If you don't do the work now, you do it later. An email that goes unanswered for 10 minutes doesn't disrupt the flow of emails. Office workers are probably overscheduled, so a good chunk of your time at the office isn't productive. You're just there in case something comes up, not becaue there's actually 8 hours of typing to do that day.