A lot of that was in warehouses (I also worked in greenhouses harvesting cucumbers 45C and 100% humidity, a paint factory moving 15l paint tins all day - never eaten so much or been so fit, 15l tins of bitumen are heavy to handball all day, steel plant that powder coated so hot tanks of acid and full PPE and a cardboard box factory) and almost nothing I’ve read about amazon surprises me much.
Warehouse work is often physically demanding and rote, same thing over and over again, I never had a problem with that because I’d just go on autopilot and the day would pass in a blur - never had an issue with hard work and got multiple full time offers, I’ve always been a naturally hard worker, I always figured I’m here for 8-12 hours day goes faster when you are busy.
It was an interesting experience and after moving into enterprise software development served me really well when it came to producing things operatives actually got a benefit from.
It also makes me think that TUI’s with shortcut keys are often massively more efficient than a pretty GUI but I digress.