They are afraid of being disciplined for idling and losing their jobs as a result. The warehouse resembled a prison or an airport, with high security scanners that check workers for banned items like hoodies, sunglasses, and phones, and other employees who pat down workers to check for stolen goods.

These are excerpts from the book Hired: Six Months Undercover in Low-Wage Britain written by journalist James Bloodworth, who went undercover as an Amazon worker for his book.
55% of the workers report having suffered depression since working at Amazon (UK) warehouse