Thread:The S/@comment-995426-20180325082311/@comment-995426-20180327024911

There's a good reason for that restriction: The preservation of article edit histories. Ordinary users can create new articles or rename articles to unused names, as a new article has no prior edit history, and existing edit histories are moved along with article renamings. But it would be a bad thing for unelevated users to be able to rename articles to existing names, even if the existing name is itself just another redirect, because even existing redirects have article histories, and it would be bad for anyone besides an administrator/moderator to be able to unliterally destroy a whole edit history. It's the same reason why only administrators/moderators can do true rollbacks of series of edits and remove them from the edit history: The power to fundamentally alter existing edit histories (rather than merely add new items to them) must necessarily be a privileged operation. It's about preserving every step of a page's history and its list of contributors, which is especially helpful for administrators/moderators if you need to police pages from erroneous edits, inappropriate edits or outright vandalism.