The reason why EndeavourOS installs r8168 by default is in fact very simple: if the system already has r8168 in the package cache, user has an easy way to try 8168 or 8169 by either uninstalling or installing r8168. No internet connection is needed to do that!
If we would not install r8168 by default, a user without an internet connection (with 8169) might not be able to download r8168…