TheChampionOfTime wrote: If a category is added to page, there must be evidence on the page that there is a reason the page has that category.
Sigh, that's the ideal. The sad reality is that some users love to add categories to pages (I blame the Game of Rassilon for that), and rarely do they check for redundancy, existence of the category, or whether the information is on the page. In addition, few users even read the descriptions located on category pages. The descriptions are usually only read by those who already know how to use our category system.
From an admin point of view, it's better to not allow something that would require extra cleanup. We have so few people (admin or otherwise) who are able and willing to clean up after other editors. We have to minimize as much as possible the extra work.