Last I knew, most businesses like that have "side work" to do. That can include making sure there are supplies (envelopes, etc.) in the front cubbies, pens that work, and that everything is counted. Plus, I have heard the expression many times "If you have time to lean, you have time to clean". Very rarely do employees actually end up in a pickle with nothing to do.
It's the same everywhere. I have seen cashiers that are busy at supermarkets. Even with no one in line, they have to be prepared at any time--if there are people shopping, they have to wait for the customer to come to the line. Plus, there is side work--newspapers to sort, belts to clean, the scanner to clean, making sure there are supplies on hand, and stocking the register displays. It would seem to me that, in order to have time to read the Bible, it would have to be very slow for a protracted amount of time, all sidework done, and they are expecting to get busy later.