I wonder if more people might desire this feature now that Discourse may work well with a lot more categories:
For myself, I’m imagining hosting a forum that has chapters in maybe over 100 countries and maybe other types of categories as well. While it could be done with tags, I like the idea of each country being able to manage its own subcategories without having to ask the admins/staff manually each time because I think category management gives more control over who can view/reply/create than tag management does.