Plugin directory NO usage/function based classification?

The current wordpress plugin directory is mainly tag-based. Also some hit-based and date-based. I wonder why there is no usage/function based classification?

I had spend a day or two to search for a plugin, which can bind some user to certain categories. That means he/she can only see and post in that category. But when I used the tag-based classification, lines of unstructured tags ware listed one by one with no sense of beauty. It’s difficult to quickly find the right tag one needed. Not to mention the search by keyword. I used category, user, role and other keywords, but no proper plugin. Until I used Restriction as the keyword. Then I founded the “Restrict Categories”, which fits my needs properly.

In fact, different tags or keywords lead to different search results, but how can you find the right tag/keyword each time? Why NO usage/function based classification?