I don't know it they are CO2 inflated or just foam-filled. But if they are worn, they must be folded and inspected before being returned to the rack. It is like merchandise in a store, like clothing that you try on, the employees must fold them properly and put pins in them before putting them back on the shelf or hanging them on the rack.
You can see that if all the life vests are taken down, when the boat comes in, it has to be prepped before the next load of passengers get on. Schedules get behind.