Usb printers are hard to monitor. (why-usb-printers-are-a-wreck)
Our client asked us to monitor 100+ printers from a Hospital. All printer where locally connected to a PC to avoid private information going into the net. All printers where located in different offices, some of them were accessible only during certain hours and different people had access to them depending on the area. In short, taking meter readings was a nightmare.