Deletion requires some care: an administrator has to check that the prod tag has been on the article for 5 day continously, that the prod'ed version was not the result of vandalism, that the prod reason is acceptable (possibly checking the talk page), then has to delete the article reporting this reason, possibly deleting the talk page, and finally checking the incoming links. Before starting doing this on every article in the category this adimin relies on the number of categories instead of calculating five days to today?