There are possibly no volunteers active today there.
Who knows where each volunteer will be active tomorrow?
Editors aren't managed like cattle--herded off to graze in the North Forty today, then moved to Slag Gulch tomorrow. Within the limits of his demonstrated proficiency, each editor is free to choose which categories to work in, and what to do there.
There are a few thousand active editors, and a few hundred thousand categories. So most categories are maintained by the active volunteers who (at any particular time) are 99% likely to be working on some other category.
