The everyone group is very helpful if you have a lot of user groups. You can basically set 1 group that sets all groups, but it loses it's usefulness and virtually becomes useless if like most sites you plan to limit guest. Because if you approve it in the everyone group, it currently will bypass whatever you have approved or disproved in the guest group
So if I have 12 user groups, I want to be able to use the everyone group for simplicity. But I also want guest to be restricted, but the everyone group counts everyone. So now it's useless to me and I end up having to configure all 12 user groups independently, having disabling the everyone and also having to disable the guest.