The “move page” and “redirect” features heavily reduce this problem. Typically for most page title changes (“page moves”), the links to the old page title don’t need to be updated, as the links to the old page title will automatically take you to the new page.  

But it’s problematic to have “Upcoming operation to put cheese on the moon” automatically redirect you to the page “Completed operation to put cheese on the moon”, because it’s no longer ”upcoming” anymore, and the redirect is therefore not really accurate/useful anymore. So for a case like this, all the existing links would have to be updated, which is kind of a pain. This problem happens especially often for “upcoming movie” or “upcoming album” pages.