/etc/default came from, and it's basically a vestige of when distros used sysvinit for managing servicesnot sure why grub of all things decided to put their bootloader config in there too though
/etc/default came from, and it's basically a vestige of when distros used sysvinit for managing services/boot/grub/grub.cfg or similar) but often times it's /etc/default/grub that's configured by the admin and grub.cfg itself is often advised to not mess with.