These would tyypically be purchased for larger installations.
Advantages of using them are:
- Security: The ability to lock away your servers so that not just anyone can turn off vital hardware or disconnect cables as they please.
- Organisation: The alternative being PC boxes and servers lying all over the floor.
- Space saving: Because your hardware is stacked vertically from the floor to the ceiling you maximise floor space.
- Water damage: Because not all of your servers are at floor level you will only lose a few should the worst happen.
- Convenience: You can easily move multiple servers around thanks to them all being installed in one or two racks with wheels.