> My understanding is that default unit files provided by the systemd packages are in /usr/lib where they can be read-only, whereas users can add/override them by dropping their own unit files into /etc (which is more likely to be read-write).

> This provides a clean separation between the default configuration and the user configuration.

> Can you explain why this is a bad thing?

The normal way to do this is to put the default configuration in /usr/share/.