The hostname of a Linux system is important because it's used to identify the device on a network. The hostname is also shown in other prominent places, such as in the terminal prompt. This gives you a constant reminder of which system you're working with. It's a real life saver when you're managing multiple systems through SSH and those command line terminals start to blend together in your mind.
This is a companion discussion topic for the original entry at https://linuxconfig.org/how-to-change-hostname-on-debian-linux