Thread:D3X1K AXYZ/@comment-410526-20141020111549/@comment-10380701-20141020121451

A  category is unnecessary categorization, it only serves to clog up the categories database, since in theory, all the things you categorized under Ruby Rose, for example, can be found in her profile already. In general, people prefer to look at the page than the categories.

That's why it's unnecessary.