Administrators can protect the page fully but only if it is necessary and not used for their own selfish reasons. Here are some main reasons why the page has been locked fully.
Editors are adding so many spoilers which that aren't evenly true.
Editors are adding false information constantly.
An edit war has been taken place to the page.
It can also be that the administrator is testing out some new layouts or templates currently on the page, which must not be disturbed.
Some pages are not meant to get edited by editors, such as the policy and main page.