The motivation is that variants of the same distro that share the same compiled rpm want to customize various aspects of the system, in particular the hostname. In some sense the default hostname is part of the identity of the system, so setting it through os-release makes sense. In particular, instead of setting a default value in /etc/hostname, the appropriate default can be baked into the image, leaving /etc/hostname for local overrides only. Why make this a separate field instead of e.g. using NAME from os-release? NAME is already used for other purposes, and it seems likely that people want to set those independently.
System and Service Manager
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