At a school or university there could be dozens or possibly hundreds of projectors scattered around the campus so the ability to quickly check remotely that each projector is performing satisfactorily is important. There may also be times where you may want to control multiple projectors simultaneously without reaching for the factory remote control.
Once you have connected a compatible projector to your network, you can control it using a web browser. This allows you to access the projector remotely and control things like focus, zoom, shift, and test patterns. You can even set up a networked projector to send you an e-mail alert if there is a problem. The email will list the name of the projector experiencing a problem and detailed information about the issue. In addition to being able to control a projector via a web browser, some manufacturers offer software program options which can be used to monitor and control the projector.
In addition to control software offered by the manufacturer, many business/installation and education class projectors are also compatible with 3rd party control systems such as the Crestron RoomView network monitoring and control system, which also allows you to setup and adjust a networked projector.
DMX is an older command and control system that is best known for controlling lighting. DMX is still used heavily today for stage work and in classrooms. It is still a viable solution for theaters putting on live shows and concerts.
With DMX Art-Net, projectors can be controlled/automated along with the rest of the lighting which can be a powerful way to tackle things like projection mapping (which is utilized in many concerts these days).